when you say TR and Zwift can’t find the dongle, what do you mean? Do you mean ANT+ is greyed out in either or do you mean you aren’t seeing those ANT+ devices in your list of devices?
I have had this issues before when it was the devices. I would check in the Computer Management area and the devices weren’t showing up in the list. plugging and unplugging them and restarting the computer helped every time, but that assumes the dongles aren’t recognized. If it’s the devices that the dongles don’t see, that could be interference, it could be distance. I have both my dongles on an extender to get within a couple of feet of my trainer.