Hello @barmeyPhil 

Sorry for the late update. 

1.  Use WPA/WPA2-PSK as Wi-Fi security on router

2. create an unsecured Guest Wi-Fi with no password and see if  computer with T2U could connect to it

3. Create a Hotspot WiFi on the mobile phone with simple password, and see if adapter could connect to it

4.Double-check the WiFi password of router, remove old WiFi profile on Windows computer, manually reconnect Wi-Fi by put in Wi-Fi password again
https://www.tp-link.com/en/support/faq/918/

You could verify password by forget Wi-Fi on the photo and manually reconnect to router Wi-Fi 

If still the same issue, can you help confirm information here:

1.    model of router
2.    a photo of the WiFi settings on router
3.    is the issue is 2.4Ghz wifi or 5Ghz wifi 
4.    photo of motherboard information and driver version : https://www.tp-link.com/support/faq/2722/