I have the same problem, I am using 3DR PX4 with QGC and recently updated to the latest firmware suggested. I use Taranis Q X7with X8R on SBus mode. I connected properly.
The problem is whenever I use USB I can get the board connect to the RC, but if I plug in the power, the RC stops moving. Thus the calibration never get completed.
This problem persists even though I tried flashing it, factory reset or even change to mission planner.
I worry it is a hardware problem? Or may be there is something I can do to save my board?