I’ve come across an issue with the FTDI USB adapter with Zwift. If you should unpair your Computrainer, it will not find the Computrainer for repairing when you search. You will have to remove the FTDI and reinsert it into the USB port. After a couple of seconds, the Computrainer will be paired with Zwift.
I uncovered this issue while I was trying to use my Bluetooth HRM (Wahoo Blue) for HRM but Computrainer for power and cadence. With the FTDI in the USB port, you will not be able to pair with any Bluetooth sensor. To work around this problem, unplug the FTDI and restart Zwift. Ensure that Bluetooth is enabled on the PC. Start the Zwift mobile app on Smart phone. Start the Zwift app on PC and hit search button under HRM plaque. Note, the Bluetooth beacon (upper left corner of the the screen) must be active (radiating circles). Search should find your BT HRM and pair with it. Now re-insert the FTDI and after a couple of seconds, the Computrainer should be paired with power and cadence. The HRM should remain paired via Bluetooth.