Hello @ucira

• If adapter fails to connect to Wi-Fi network, try to remove Wi-Fi profile (delete the old Wi-Fi network) on your settings, and reconnect to it. 

How to connect to wireless networks and remove its profile on Windows 10

• Ensue you have put in correct Wi-Fi password,  test the same wifi password on your mobile phone. 
• Ensure you have installed the latest driver for TL-WN881ND
• Try a different wifi channel on the main router
• For test purpose, you could create a Guest wifi network without password and see if the adapter can connect to the open wifi network. 

If still the same, may I know, did you recently update the Windows version , what is the error message when failed to connect to wifi network, can you share aphoto of it?