If you're pairing your TrueBike with Zwift, there's 3 channels available:
1. Power meter
2. Cadence sensor
Some phones and tablets support ANT+, most of these devices however only support incoming ANT+ data, and lack the function to send ANT+ data. This means the controllable channel won't work.
To solve this issue, make sure all connections are paired to bluetooth. You can check this by tapping the connection and checking the logo to the right of the device name.