Ethernet working but not wifi

I can access Internet via Ethernet port to my Xfinity box, but no WiFi access for devices in range of my router. Tried power cycling and rebooting laptop multiple times and resetting the gateway.

Also, I have a wired Ethernet connection to another room that is connected to an Airport Extreme. I can connect to WiFi on laptops and phones that are close to the Airport, but when am on the side of the house near my Xfinity box, I can no longer connect to WiFi (doesn't see the network). I can walk around the house and the wifi link will connect or disconnect depending on whether I'm in range of the Airport.