TP Link TL-WN821N?

I assembled a PC and I also got the WLAN stick described above (used by a friend). When I wanted to install a game it worked first but suddenly the stick was no longer connected. Or if I e.g. He is no longer connected to Minecraft. Can someone tell me how to solve the problem?

There must be an access code in the stick, enter it again and go to Connect.

If you have Windows 10, go to Internet Settings, then Wi-Fi and uncheck "Use online registration to connect" below.