I’m not sure if re-installing on the PC will help, but it should not cause harm. If you want to do that, follow these instructions: Re-Installing Zwift
There was another recent discussion about this topic here: Justo 2 virtuel shifting not works - #21 by Mike_Devuyst
You must also ensure that Zwift is not running on both the phone and the PC at the same time. Do not swipe Zwift into the background on the phone. It must be terminated so the trainer will not be controlled by a second copy of the game, or anything else such as an Elite app.