Tried to Zwift this morning. Zwift disconnected from my Kurt Kinetic trainer and Wahoo HRM while I was selecting my workout on my Apple TV 4k. No amount of restarts would get them to connect. Changed out all my device batteries with new ones. Nothing. Turned off Apple TV, installed on my iPhone - won’t find trainer or HRM. Turned off phone. Installed on my iPad - won’t find trainer or HRM. Turned off iPad, turned on my Wahoo GPS for outdoor riding - trainer, HRM, speed, cadence, everything connects immediately, full strength. Why is Zwift Bluetooth LE support on Apple so bad? So frustrated.
Have you tried using the companion app to bridge the signal?
I started the Companion App while selecting a workout and think it may have caused the dropout. I had all devices connected when I went into workout selection, but when I started the workout, I had no HR, no pedal response, just stuck in one spot. Hasn’t connected to any device other than my Wahoo Element Bolt since. 
Is the wahoo app running on the phone in the background maybe? Force close everything to be sure.
Ok, unistalled Zwift from Apple TV, reinstalled. Was then able to reconnect. Strange, but at least it’s working again.
Keep in mind that the Apple TV will only connect to 3 BTdevices. So controllable trainer, HRM, Apple TV Remote as an example.