Questions about automatically connecting to the trainer

My default power source is the power meter.
Every time I turn on Zwift, it cannot connect to the trainer automatically. I have to manually switch the power source to connect to the trainer.
WHY ????

Hi @Bin_Tian

Welcome to the forum.

The controllable part of the Trainer only become active once the trainer power source is connected, that is how the trainer protocol is programed on the trainer.