Position and Speed are the control modes I'm talking about. You must be in one of these modes for there to be a ClosedLoopError. How else will the Talon know whether to calculate ClosedLoopError in position or in velocity?
If you are selecting PercentVbus, then the Set() calls will simply control the output voltage of the Talon (no closed loop). And CloseLoopErr will not change since Talon won't calculate it.
What errors did it give you? Maybe rebuild the index?
https://wpilib.screenstepslive.com/s...ildingTheIndex