Had this same problem with my Elite Qubo Digital Smart B+. Stumbled on an exchange on another related forum post, wherein a support team member mentioned that for a smart trainer, the power and smart trainer connections must be set to the same device in order for FE-C (which controls the resistance) to work. Now, the Elite Qubo Digital Smart B+ shows up as three separate sensors for me:
- Elite PWR
- Elite RealTrainer, and
- Elite FE-C
What you’re going to want to do is set both the “Power Source” (top left corner in the Zwift desktop interface for Windows) and the “Controllable Trainer” connection (bottom right) to Elite FE-C. Again, FE-C is the type of ANT+ connectivity that allows for two-way communication, so you can control the resistance.
So, give that a shot, crank the trainer sensitivity up to the max in the settings, and give the mountain loop a try. Worked for me.