Network troubleshooting technician providing live chat help

Joe B.

Expert ★★★★★ 27,853 satisfied customers

Specialities: Home networking, Wi-Fi modes (802.11b/g/n/ac/ax), legacy device compatibility, smart home & IoT Wi-Fi issues, router security (WPA2/WPA3)

Fix device not connecting after changing Wi-Fi mode (b/g/n/ax) — Wi-Fi 4/5/6 compatibility & 2.4 GHz vs 5 GHz

Technician avatar Technician
Hi! We’ll sort out this device not connecting after changing Wi-Fi mode (b/g/n/ax) problem and get everything talking to your router again.

To start, what exactly did you change on the router — the Wi-Fi mode (802.11b/g/n/ax), the band (2.4 GHz vs 5 GHz), the security type (WPA2 vs WPA3), or the channel width (20/40/80 MHz)?

Which devices can’t connect now (for example, smart TV, Wi-Fi printer, smart plugs, older phones), and which ones still work (newer phones or laptops)? Do the failing devices show something like “unable to join network”, “incorrect password”, or they just spin when trying to connect?

The more detail we have about your Wi-Fi 6 / 802.11ax router and the devices that broke right after the change, the faster we can adjust the b/g/n/ax mixed mode and security so everything connects again.
Customer
I just upgraded to a Wi-Fi 6 (802.11ax) router. In the 2.4 GHz settings I changed the mode from 802.11b/g/n mixed to 802.11b/g/n/ax mixed and also enabled some “AX only” option on 5 GHz.

Since then, my older HP Wi-Fi printer and a couple of smart plugs won’t connect. My iPhone and laptop are fine on both bands, but those older 2.4 GHz devices either say “can’t connect to this network” or just time out. I didn’t change the network name or password, only the Wi-Fi mode and security to what the router called “WPA3-Personal”.
Technician avatar Technician
Thanks, that’s exactly the info we need.

In theory, 802.11ax (Wi-Fi 6) is backward compatible with b/g/n, but in real life a mix of settings can cause older 2.4 GHz devices to drop off as soon as you change Wi-Fi mode:

• Some legacy devices only understand 802.11b/g or 802.11n (Wi-Fi 4) and choke when the 2.4 GHz radio is set to an aggressive b/g/n/ax mixed mode or “AX only”.
• Many printers, smart plugs and cameras don’t support WPA3 at all — they need WPA2-PSK (AES) or a WPA2/WPA3 “compatibility mode”. If you go WPA3-only, they simply refuse to connect. :contentReference[oaicite:0]{index=0}
• Wide channel widths (40 MHz on 2.4 GHz) or “auto” settings can make the network vanish or look unstable to old chipsets.

We’ll tune your 2.4 GHz Wi-Fi for maximum compatibility so those devices can rejoin, without ruining speed for your newer Wi-Fi 5/6 devices.
Customer
That sounds right. The router now shows:
• 2.4 GHz: mode 802.11b/g/n/ax mixed, channel width 40 MHz,
• Security: WPA3-Personal only,
• 5 GHz: 802.11ax only with band steering so both bands share the same SSID.

My newer devices connect fine, but the printer and smart plugs can see the Wi-Fi name, ask for the password, and then fail with “unable to connect”.
Technician avatar Technician
Perfect, we’ll start by making a “friendly” network for those older devices.

Step A — Create a 2.4 GHz legacy-friendly network
1) In your router’s Wi-Fi settings, split the bands so 2.4 GHz and 5 GHz have different SSIDs (names). That makes it much easier to aim older devices at the right band.
2) For the 2.4 GHz band, set the mode to 802.11b/g/n mixed (disable ax/“Wi-Fi 6” on 2.4 GHz for now). This keeps compatibility with Wi-Fi 4 devices that can’t handle 802.11ax.
3) Change security on 2.4 GHz to WPA2-PSK (AES) or “WPA2/WPA3 mixed” rather than WPA3-only so legacy hardware can authenticate. :contentReference[oaicite:1]{index=1}
4) Set the 2.4 GHz channel width to 20 MHz. Many IoT chipsets are more stable on 20 MHz than 40 MHz.
5) Keep 5 GHz as 802.11ac/ax for your modern devices, but it’s okay if that band stays on WPA3-Personal.

After saving these changes, try connecting one smart plug and the printer specifically to the 2.4 GHz SSID we just configured.
Customer
I separated the SSIDs and changed 2.4 GHz to b/g/n only with WPA2-PSK and 20 MHz. Now the printer can actually see the new 2.4 GHz network and tries to connect, but it still fails the first time. A couple of smart plugs connected on the second try though.
Technician avatar Technician
That’s a good sign — the basic b/g/n compatibility is working now, we just need to clean up saved settings on the devices.

Step B — Reset the device’s Wi-Fi profile
• On the printer, go into its network or wireless menu and choose “Reset network settings” or “Restore Wi-Fi defaults”, then set it up again from scratch and pick the new 2.4 GHz SSID with WPA2.
• On each smart plug, hold the reset button until it enters setup mode, then use the app to connect it to the 2.4 GHz network only (most apps say “2.4 GHz Wi-Fi required”).
• If your phone is on the 5 GHz / Wi-Fi 6 network while you’re adding devices, some apps get confused. Temporarily connect the phone to the same 2.4 GHz SSID when onboarding smart plugs and bulbs.

After that, we’ll see if any devices still refuse to connect after the Wi-Fi mode b/g/n change and we’ll handle those individually.
Customer
Resetting the printer’s network settings did the trick — it connected right away to the 2.4 GHz WPA2 network. All smart plugs are back online too.

Now my iPhone complains that the 2.4 GHz network has “weak security” because it’s on WPA2 instead of WPA3. Is it okay to leave it like this just for those older devices?
Technician avatar Technician
That “weak security” warning is common when you mix modern phones with older hardware.

A practical setup is:
• Keep the 2.4 GHz b/g/n network on WPA2-PSK only for printers, cameras, smart plugs, thermostats, and other legacy or IoT devices that can’t use WPA3.
• Keep a separate 5 GHz Wi-Fi 5/6 (802.11ac/ax) network with WPA3-Personal (or WPA2/WPA3 mixed) for your phones, laptops, and tablets.

That way you fix “device not connecting after changing Wi-Fi mode” without having to downgrade security for your entire home. If you ever replace those old devices, you can bump the 2.4 GHz band to WPA2/WPA3 mixed or even WPA3-only later on.
Customer
Makes sense. One more question: in the router there are options like “b/g only”, “b/g/n”, and “b/g/n/ax mixed”. Is there any reason to use the b/g/n/ax mode on 2.4 GHz if everything works now, or should I just leave it at b/g/n for compatibility?
Technician avatar Technician
Great question — this is exactly where people run into device not connecting after changing Wi-Fi mode (b/g/n/ax).

• On 2.4 GHz, the sweet spot for most homes is 802.11b/g/n mixed with 20 MHz channels. That’s compatible with nearly everything and still fast enough for printers and smart home gear.
• On 5 GHz, you can safely use 802.11ac/ax and wider channels (80 MHz) because that’s where your laptops and phones benefit from Wi-Fi 5 and Wi-Fi 6 speeds. :contentReference[oaicite:2]{index=2}
• Using b/g/n/ax mixed on 2.4 GHz sometimes causes strange edge-cases with older chipsets and IoT firmware. If you don’t have any 2.4 GHz devices that explicitly need 802.11ax, staying on b/g/n is usually more stable.

So yes — keeping 2.4 GHz at b/g/n and reserving ax for 5 GHz is a good long-term strategy.
Customer
Got it. The last annoyance is when I add new smart bulbs: the app keeps saying “make sure you’re on a 2.4 GHz network” and sometimes fails if my phone sticks to 5 GHz. Is there a trick for that, or is it just trial and error every time I change Wi-Fi settings?
Technician avatar Technician
You’re not alone — that’s a classic 2.4 GHz only IoT headache, especially after switching to a Wi-Fi 6 / 802.11ax router.

A few tricks:
• While setting up bulbs, temporarily connect your phone to the 2.4 GHz b/g/n SSID (not the 5 GHz / ax network). Some apps won’t even start pairing if the phone is on 5 GHz.
• If your router supports it, you can temporarily disable the 5 GHz band while onboarding a batch of smart devices, then turn it back on once they’re added.
• Keep the 2.4 GHz SSID name short and simple (letters and numbers only) and avoid emojis or special characters — some cheaper IoT devices can’t handle them.

With your bands split and Wi-Fi mode b/g/n locked in on 2.4 GHz, future devices should connect much more reliably without surprises when you tweak Wi-Fi modes again.
Customer
That all helps a lot. So far everything is stable: old printer, smart plugs, bulbs — all online — and my newer devices are happily using the faster Wi-Fi 6 network. Anything else I should do so I don’t break it again the next time I change settings or replace the router?
Technician avatar Technician
Great question — prevention means you hopefully never see “can’t connect after changing Wi-Fi mode” again.

Step C — Make your Wi-Fi setup future-proof
• Take screenshots or notes of your working settings: 2.4 GHz = b/g/n, 20 MHz, WPA2-PSK; 5 GHz = ac/ax, WPA3 or WPA2/WPA3, separate SSIDs, etc.
• Before enabling new features (for example, turning on “AX only” or WPA3-only everywhere), test them on the 5 GHz band first and leave the 2.4 GHz “legacy lane” alone.
• Update router firmware regularly — some versions fix bugs where devices randomly disconnect when you use b/g/n/ax mixed mode or advanced power-saving features. :contentReference[oaicite:3]{index=3}
• If you ever swap routers, recreate this same layout (2.4 GHz legacy, 5 GHz modern) instead of relying on the default “smart connect” band-steering modes that often break older devices.

If anything ever acts up again after a Wi-Fi change, you can always open a chat with an expert and we’ll walk through the modes and bands with you live.
Customer
Awesome, everything’s working and I understand what not to touch now. Thanks for walking me through all the Wi-Fi mode and compatibility stuff.
Technician avatar Technician
You’re very welcome — nice work getting everything reconnected.

Quick recap: when you hit device not connecting after changing Wi-Fi mode (b/g/n/ax), the fix is to split 2.4 GHz and 5 GHz, set 2.4 GHz to b/g/n + WPA2 for older and IoT devices, keep 5 GHz for Wi-Fi 5/6 with WPA3 if you like, use 20 MHz channels on 2.4 GHz, and reset Wi-Fi profiles on stubborn devices.

If a friend upgrades to a new Wi-Fi 6 router and their printer or smart plugs suddenly can’t connect, you can share this checklist — or just start a chat with an expert and we’ll tune their Wi-Fi mode b/g/n/ax settings for them.

Quick answer: the accepted fix

Accepted fix when a device is not connecting after changing Wi-Fi mode (b/g/n/ax): split 2.4 GHz and 5 GHz into separate SSIDs, set 2.4 GHz to 802.11b/g/n mixed with 20 MHz channel width and WPA2-PSK (AES) or WPA2/WPA3 mixed, keep Wi-Fi 6 / 802.11ax and WPA3 on 5 GHz for newer devices, then reset or “forget” the network on affected printers, smart plugs, and other IoT devices so they reconnect using the new, compatible settings.

Why devices stop connecting after changing Wi-Fi mode (b/g/n/ax)

When you change router Wi-Fi mode from b/g/n to b/g/n/ax, enable Wi-Fi 6, or switch to WPA3-only, older hardware can suddenly refuse to connect. Many printers, smart plugs, cameras and smart TVs only understand 2.4 GHz 802.11b/g/n with WPA2-PSK, and they fail silently if the router tries to talk 802.11ax or uses encryption they do not support.

This is why a device not connecting after changing Wi-Fi mode (b/g/n/ax) is so common right after a router upgrade. The good news is that you usually do not need to buy new hardware — you just need to adjust the 2.4 GHz band for compatibility and leave the fast Wi-Fi 5/6 settings on 5 GHz where your phones and laptops benefit most.

How to tell if the issue is Wi-Fi mode, band, or the device itself

To quickly narrow down a device not connecting after changing Wi-Fi mode problem, compare how different devices behave on each band. If newer phones and laptops connect fine on both 2.4 GHz and 5 GHz but an older printer or IoT device fails only on 2.4 GHz, it usually points to b/g/n/ax mode or security compatibility rather than a general internet fault.

Try creating a temporary 2.4 GHz network set to 802.11b/g/n with WPA2-PSK (AES) and 20 MHz channels. If the problem device suddenly connects there, you’ve confirmed that the previous Wi-Fi mode / WPA3 settings were the cause. If it still will not connect to any correctly configured 2.4 GHz network, the issue may be specific to that device’s Wi-Fi adapter or firmware.

Device not connecting after changing Wi-Fi mode — quick troubleshooting tips

Create a 2.4 GHz “legacy lane” and keep Wi-Fi 6 performance on 5 GHz.

Fast path: split 2.4 GHz and 5 GHz into separate Wi-Fi names → set 2.4 GHz to 802.11b/g/n, 20 MHz, WPA2-PSK → leave 802.11ac/ax and WPA3 for 5 GHz → reboot the router → reset Wi-Fi on problem devices (forget network or run their network reset) and reconnect them to the 2.4 GHz SSID. This combination fixes most “device not connecting after changing Wi-Fi mode (b/g/n/ax)” situations without sacrificing speed for newer devices.

Disclaimer: This information is AI-generated and intended for general guidance only. For advice specific to your router model and devices, please consult a verified expert on Whizz-Tech before making decisions.

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FAQ

Why did my device stop connecting after I changed Wi-Fi mode to b/g/n/ax?

Most of the time, the device only supports 802.11b/g/n and/or WPA2-PSK. When you enable 802.11ax on 2.4 GHz or set the router to WPA3-only, older chipsets and IoT devices see the network but cannot understand the new mode or encryption, so they fail to connect even though the password is correct.

How do I fix an older 2.4 GHz device that won’t connect to a Wi-Fi 6 router?

Put your 2.4 GHz band into 802.11b/g/n mixed mode, set the channel width to 20 MHz, and use WPA2-PSK (AES) or a WPA2/WPA3 mixed mode. Give 2.4 GHz its own SSID and point the older device to that network. If it still fails, reset the device’s network settings and reconnect it as a fresh setup.

Should I use b/g/n/ax mixed mode or just b/g/n on 2.4 GHz?

For maximum compatibility, especially with printers and smart home gear, b/g/n is usually the safest choice on 2.4 GHz. You can reserve ax for the 5 GHz band where your newer phones and laptops connect. Using b/g/n/ax mixed mode on 2.4 GHz sometimes triggers odd behavior in legacy devices.

Is it safe to use WPA2 instead of WPA3 so old devices can connect?

WPA3 is more secure, but many older devices do not support it. A common compromise is to have a WPA2-only 2.4 GHz network just for legacy and IoT devices and a separate WPA3 or WPA2/WPA3 network for newer devices. That way you fix compatibility without lowering security everywhere.

Sources

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