I just set up and registered a brand new TTN Gateway with a Wifi connection. I can successfully send uplink and downlink messages from a Things Uno and Things Node. Every few hours, the Gateway drops the wifi connection and goes into AP setup mode with the setup SSID and a slow or fast blinking LED2. Sometimes, it recovers on its own and sometimes I reboot the Gateway and it starts working again. The Gateway location has great Wifi coverage with other devices.
In the meantime, I hooked up the UART in the Gateway to my computer and will see what shows up when the Wifi drops off again.