Why can't I get an internet connection on my PC?

I bought a PC on ebay. It actually works perfectly just somehow the WLAN doesn't want to.

A LAN connection is not possible in my room, so I bought a TP-Link wireless USB WLAN adapter. After the installation, the networks in my area were shown to me as usual, only when I want to connect it always says "No connection to this network possible". It is NOT on the USB stick, because I had done the same on my laptop and everything worked perfectly there. I don't think it is due to our WLAN either, because my PC apparently has the same problem with my cell phone hotspot, because here it only said "No connection to this network possible".

I've already tried a lot and tried all the options that I found on the Internet, but nothing turned out to be helpful.

I'm a little desperate, so if you have any ideas, please write them!

Look whether there's an exclusion list for devices in the WLAN (whitelist). Then you have to enable the TP link in the router settings for WLAN.

Is access restricted to certain devices in the router? Can I assume the correctly entered network key?

Also look in the router log under WLAN to see what is there.

The PC doesn't even connect to my mobile phone hotspot, which has no password or anything else.

Then look for a tutorial on YouTube for your USB WLAN stick model, maybe you will find a mistake on yours.

The password is not a problem. Even with my open cell phone hotspot, he doesn't want to.