Hi all, I'm having a very strange issue with my Archer AX12 router. Some devices on WiFi do not seem to be able to connect to the Internet.

I purchased it in December 2023 and have had no problems with it. That is, until recently and seemingly at random, it stopped letting WiFi devices connect to the Internet. I thought this very strange, and after checking the settings [which I had not changed], I could not see any obvious issues, so I proceeded to reset the router and after setup, it was still doing the same thing. Ethernet devices were connecting just fine, but not WiFi. To be clear, some WiFi devices were not connecting [and in fact, I was typing this up on my laptop when it stopped functioning properly, but now after checking my laptop again, it's working again].
 

After some further digging, I found the IP and Gateway assigned to these devices were wrong. The address I had set for the router/Gateway was 192.168.69.1 with DHCP enabled, while the devices without Internet were being given 192.168.0.254 [and an IP address to match that range]. So I on my phone [Pixel 7a], I set a static address and Gateway, etc to no avail, so I changed the router settings to suit and it still wasn't working properly [even after forgetting the WiFi]. I also thought maybe it was a conflict with my Powerline adapter in a mesh network with the router, but it's unplugged right now and this is still not working as expected.

Like I said, some devices have been able figure this out, some do not. My housemate's iPhone [14 or 15, not sure] and Nvidia Shield are among those that cannot resolve this, while my own phone can [although now, it cannot - even with the settings set to the options the devices seem to want]. Likewise, my tablet [Samsung Tab A8] was able to figure it out, but not any more. And the Ethernet devices [the PC I'm currently on, my own Shield along with the aforementioned Powerline kit prior it unplugging] all connect just fine.

Beyond the basic settings [like ISP, admin access, WiFi access like SSID and password, DNS servers, along with the settings above], everything is default. Firmware is up-to-date and the it is a FTTH connection. All devices to the best of my knowledge are up-to-date and [those that can] can connect to other WiFi.

Any assistance is greatly appreciated.