I just installed a new ArcherT4E in exchange for an older TP-Link adapter, hoping I would be able to connect to the 5GHz band of my FritzBox 7490 router. I can see the 5GHz connection in the wireless selection dialog. But when trying to connect I get and after entering the WPA2 key I get a "no connection to this network possible" response. The 2.4GHz side works perfectly well. I also tried to connect to the 5GHz band with my mobile phone and that worked perfectly well.

The setting "wireless mode" is on "Auto". I experimented with setting that to IEEE 802.11a/n/ac, but that didn't connect to either band and doesn't even show the 2.4GHz connection in the selection dialog.

I am on Windows 10, 64bit. The driver details are as follows:

Any guess what might be the problem?

Also: With my 10 year old TP-Link card I also got a utility that allowed some diagnostics of the card and the visible networks. The new Archer T4E just came with a driver. Is there still a utility with which I can diagnose this problem a bit deeper. Windows 10 integrated tools are very rudimentory for this.

Thanks for any help on this.