Unable to connect to 2.4 GHz WiFi band?

Question

I've been running into issues getting devices connected to the 2.4 GHz band of my router (TP-Link Archer C7). Note that 5 GHz works fine, no issues at all. Devices in question include Lenovo Y500 laptop, iPhone 6S+, Lenovo Android tablet.

I've tried adjusting the channel for the 2.4 GHz band, changing passwords and SSIDs, upgrading router firmware, router factory reset, all to no avail. Something weird that I'm noticing is that when I try to connect to the default SSID (TP-LINK_FB60) on my iPhone it has two separate behaviors:

• Enter correct password: Popup says "Unable to connect to TP-LINK_FB60", then after tapping confirm another popup says "Unable to connect to LAN Before Time 2" (that was my SSID before running into troubles and resetting to factory). Why would it do this? Does it recognize the router and remember past SSIDs despite it changing?

• Enter incorrect password: Popup says "Unable to connect to TP-LINK_FB60". That's it.

So there's definitely some sort of conflict going on with the iPhone at least. For the laptop I've tried making it forget the past SSIDs, ipconfig /flushdns, /release, /renew. It can connect for short periods of time (<10 minutes).

This is odd to me, that several makes and models of devices would have this issue with that particular band of WiFi. Furthermore, this is the second replacement router after the original failed. The last one was a refurbed Linksys E4500 which had the same issue I have now (I assumed it was the router's problem).

Any ideas as to why the 2.4 GHz band in my situation is so shaky?

Router configs:

1. Concurrent 2.4/5 GHz broadcasting
2. WPA2 Personal AES
3. 2.4 GHz: bgn mixed
4. 5 GHz: a/n/ac mixed

Solution

It would appear that explicitly setting the channel width to 20 MHz has fixed my issue. Before that option was set to auto.

I live in an apartment building so I'm guess there's some serious interference going on, especially if I try to span 40 MHz in the 2.4 GHz band. Using 20 MHz I no longer have dropping connections (so far anyway), and devices that couldn't connect at all before are able to now.

Comments

[Aganju]

I had issues with multiple devices when the router was running in concurrent mode (same SSID for both bands); took me days to find. I have now set the router back to two separate SSIDs for the two bands, and it is fine again.

[The Whether Man]

I see, that interesting. I always use separate SSIDs for each band but I could see that being an issue otherwise. Thanks for the input

[Gabriel Staples]

Related: askubuntu.com/q/1196348/327339. Here's my solution: askubuntu.com/a/1271252/327339.

[The Whether Man]

I always have DHCP enabled, I'm not interested in setting IPs manually lol. The security idea is good but I had already tried disabling it completely (same issue). Thanks for your input though, see my answer if interested

[Alex Cannon]

Yeah I've seen a cordless phone completely shut down 2.4GHz Wi-Fi that was in 40MHz 802.11n mode. The older Atheros 108mbps Wi-Fi equipment automatically switches to 40MHz mode only when needed and only when there is no interference, but N doesn't do this.