We've used KASA switches and smart plugs in two houses and several configurations over the past 20 years.  Our router went offline this evening and I have been unable to get anything reconnected.  The setup app goes all the way thru to the part where the device is trying to connect to our home WiFi network. First it doesn't recognize our WiFi network so I have to type in the name and network password.  Then the app sits there spinning and after about five minutes comes back and says it wasn't able to connect.  I've rebooted the router several times and none of the devices I've been trying to reconnect tonight are mire than 12 feet away from the router.  I do get a message on occasion in the WiFi section of my iPhone settings that mentions that the network is unstable and on occasion the TP-Link network will come up in the settings on the phone and then revert to a "connected but no internet support" condition.  I haven't ever tried to get into the router configuration, but it's an AT&T router using their over the air internet package.  Thanks for any help you can give me.