I skimmed the manual and did not see any mention of a reset on that model, so bummer if leaving the power disconnected did not help. Maybe Pioneer will have info on that.
Again, I don’t know any wiring in the harness that would cause a white screen. Parking brake wire will cause a warning to pop up, and back up just toggles reverse camera input if I recall. The parking brake wire, back up wire, should not cause this, they just change what the display shows, not stop it from displaying entirely like you are getting.
Being the stereo is working otherwise, makes me think an issue to the display internally, why it happened now I don’t know. Give some time and see what Pioneer says, hopefully not just a generic reply, but who knows.