Wifi Connections Keeps Losing Internet Access

Up until two days ago, our wifi was working fine. Then all of a sudden, none of our devices can connect to internet via wifi. I've been told to reset the GW and it works immediately after (really fast) then it drops again. I've changed the channel to auto and the same thing happened: it worked for a bit then it dropped the connections. The GW shows all green lights. Not sure what to do...this is so irritating. I notice that when I open my Smart Home App, it keeps telling me the 5 GHz is disabled. I click enable but it doesn't change the connection. Is there anything else that I can look at or do to try to solve this? I've also noticed that our TV started lagging when this started. Do I just get the AT&T router replaced?