I opened a support Ticket as well already a few days ago but got only general requests back. BUT I found a workaround which enables me to use zwift even with the bug but also shows that it is not a problem with my setup, calibration or Firmware Version 
(1) Start Zwift
(2) Pairing Page opens like always
(3) Trainer is found and selected as Power resource
(4) Disconnect Trainer and connect Trainer as a speed sensor Trainer (I took anyone from the elite Trainers)
(5) Enter the game
(6) Enter the menu again and open the pairing page from the menu
(7) Now zwift connects automatically the trainer again as power resource and displays that it as disconnected the speed sensor trainer.
(8) Back to the game >>> Now it works
Hope that helps others as well to overcome this little bug. I think it shows that something is going wrong, with the normal procedure but when you repair somehow later it works.
It is a bug in the game itself and not the setup is broken. At least on my side
Peter