* The app has discovered the TV, but the screen mirroring wouldn't start?

This problem happens because your smart TV and Mac are connected to different router subnet. Please keep in mind that the first three sets of digits of your TV's and Mac's IP addresses have to be the same. For example, if the IP address is aaa.bbb.ccc.ddd, so that aaa.bbb.ccc have to be 100 percent identical.