I just wanted to share my experience in case someone else had the same issue I did.
I was fighting for several hours trying to figure out why my input wasn’t registering to rotate the springarm correctly. I was fiddling with pawn settings, default pawn settings, and finally figured out how to log information from blueprints (look for Print String).
This logging revealed to me that my input actually was registering, but still the camera wasn’t rotating.
Finally, after so much debugging, I realized that I never put the camera as a child of the springarm 
, so make sure you do that!