@Jagger 

If you have the v2 hardware version there was firmware released a couple of weeks ago to try and address random reboots which is version 1.0.5. Try to factory default the switch where the switch to where you are finally able to connect to it. Make sure the phone being used is not on a VPN connection, also that the Kasa app has local network permission (iOS), and location (Android). Rebooting the phone as well has helped in connecting to smart devices in setting it up.