BT issues relating to Zwift are beyond frustrating especially when you are dealing with multiple devices and you don’t know where to start, but you do know that the only thing that changed is that Zwift app had an update.
If it helps, the devices will show data if I DELETE or OFFLOAD the Zwift AppleTV app and reinstall it, but you can’t realistically expect us to do this on a daily basis, which is my current scenario since the update.
Sounds a bit similar to the known problem with Apple TV losing settings. Currently a drawback of running Zwift on Apple TV (but you certainly deserve a better experience).
Thank you for the link 
It’s so hard to fimd the keywords to search.
Looking forward to the fix