I have the TL-WA801ND connected to a FiberHome and set up the internet connection yesterday and it worked fine wirelessly. Later today, it stopped working and started asking for password again and connects with no internet access going through the network.
Double check that there are no loose coax connections, ethernet cable connections, or power connections on any network devices. Everything must be fully and firmly connected.
Likewise check the router's location and antenna's. The current physical configuration may be workable but at some threshold level where performance is subject to interruption/interference. You may need to experiment a bit to find a more reliable location.
Check your current configuration per the following TP-Link webpage: