@kevinkyng 

I have had the same experience with Archer T3U. I am unable to connect to the 5Ghz band (on channels 36, 44). 

I am on macOS Catalina

Version 10.15.4 (19E287)

MacBook Pro (Retina, 13-inch, Early 2015)

I am using this version of driver: https://www.tp-link.com/en/support/download/archer-t3u/#Driver

Note: The download page does mention it to be beta software. 

@mrugesh mine macOS 10.15.3 has no problem,  but Win10 1909 can't connect to 5GHz Wifi because it will auto disconnect, and I need to reinitialize my network every 5 mins to just keep it "working".  Makes impossible for a standards usage.

TP-link should do some work on their software, not release a product with unfinished drivers.

Update:

Go to router settings and change the bandwidth from 160Mhz to 80 Mhz, no more dc every 5 mins, But still dc in every 30 mins or 1 hour.

The speed also downgrade from 800+ Mbps to 585 Mbps.

This connection issue seems to be fixed for me now, while I am still not what I did to resolve the connection makes any sense.

The original issue was I could not use this Archer T3U to work on my macOS 10.5.4 (MacBook Pro, Early 2015 Retina 13") to connect to the 5.0GHz SSID for my router.

I troubleshot this by doing a factory reset my router, and now I am able to use the T3U to atleast connect to the 5.0GHz SSID, I could connect to the 5.0GHz SSID from my other devices (phone, etc.) even before resetting the router, so it does not make sense if that was related to the issues with the T3U.

However while the connection is fixed, I think I am getting terrible speeds. You would expect increased speeds from the higher bandwidth. But currently its more like what I was getting on the 2.4GHz SSID. I will report back if I find any solutions or have more updates.