It's probably not the unit, but just the float. Pull the unit out of the tank, hook it up and move the arm up and down and see if the gauge moves. If so the unit is fine. It should be pretty obvious if the float is bad, it will be full of gas. I ordered a plastic float from summit and just replaced that part. I found a thread about this on here somewhere. Says it's for a jeep but works perfectly for our application:
https://www.summitracing.com/parts/omx-1772901