Trailer Brake Going Crazy

Good morning. I hooked up my 5er yesterday and to my surprise the brake controller was going a bit crazy. It was bouncing from 1.2 to 2.3 and back down. I manually tried to engage the brake with the lever and nothing! Tried to unplug the trailer thinking it was that and nothing. Any ideas where to start? Thanks.

PS.
I have a 2007 Chevy 2500HD with a Prodigy controller.