I’m having the same issue. CycleOps Magnus and an LG G6 phone with Android 7.0. Workouts and freeride don’t affect the resistance on the trainer, despite pairing as controllable. It reads power, but the App is not controlling the resistance.
I’m emailing with support, providing log files, and I’ll try a few instructions they gave me, but I don’t think that will solve the issue. In case it helps anyone, here’s what they sent me:
Thanks for writing us.
The way you’re explaining the drop in resistance, it kinda sounds like it could be Bluetooth interference, but I’d need to take a look through your logs to be sure. If you have your Magnus paired in any other training apps or through Android’s Bluetooth settings, either could prevent data from making it from Zwift to your trainer.
When you have a moment, please restart Zwift and tap the logo on our title screen three times. You should be taken to a new screen showing two columns. Please highlight all of the files in the left column and email them to us at firstname.lastname@example.org. Please let me know here once you’ve sent them in as I’m not automatically notified.
Afterward, please log out and exit Zwift, then go into your Android settings, turn off Bluetooth, then power off your phone. Let it shut off for a minute or two, then turn it back on and re-enable Bluetooth from your Android settings once more. If you’re still noticing problems with resistance afterward, please ensure ERG is properly enabled/disabled and if that doesn’t help, I’d suggest unpairing your Magnus from Zwift’s Paired Devices screen, exiting our app, and completing an official calibration in CycleOps official support app. You’ll likely need to unpair your Magnus from their app before pairing it with Zwift again though.
Please let me know how that works out!