the only thing you can do is replace the control board, unless you can find a bad control board and pull the display off of it.

Yeah, I assume that I will have to either replace the whole board or maybe It is just the cable, since everything else is working fine. For now, I just took the temp from a submersible thermometer (right at 82 degrees). I wanted it to go up to 88, so I just slowly pushed the up arrow until the heater kicked on, then pushed it 5 more times. The thermometer now reads 88, so at least I found a temporary solution.

There was an issue with the display boards that plug into the control board. If its under warranty it should be taken care of. If not under warranty its an easy fix. if it was an older heater than there will be no display board to replace and the full control board would have to be changed