What's the version of iPhone? And what's the model of Android phone? For the laptop, how many laptops have you tested? What's the IP address on those laptops? You may try change the SSID, security,...

Can the 801ND be powered on with the power adapter? Are you using the POE adapter that comes with the 801ND? Since the POE adapter works well with others, it may be compatibility issue between the...

That's weird. I think you can send an email to tp-link tech support to get help.

What's the operating system of this computer and the other one which is working? You may try exchange the wireless adapters on those 2 computers and check whether they will work on the other...

What's the model number of the adapter? If the wireless adapter don't support 5G, you won't find it with the adapter.

The range extender have to use the same channel with your router. It cannot be changed to different ones.