Why doesn’t Oka mirror find the device I want to cast to?
Please ensure that your TV and Mac are connected to the same Wi-Fi and under the same subnet. If you still have problems when discovering your device, here are some troubleshooting tips that can help:
Restart router. Just unplug it from the power supply, wait 30 seconds, then plug it back in.
Restart the device. Unplug it from the power supply for a complete reboot. Please disconnect it from its power supply for at least 1 minute, then put it back in. Powering off your TV is NOT ENOUGH to do a complete reboot.
For possible network problems, please check How to set up the network to cast my Mac to TV wirelessly?