Keep it simple. If unplugging the power supply and removing and then putting back the LCD backup batter doesn’t work, next step would be to replace the fuse. If you’re lucky, there will be a back up fuse waiting for you in the panel you removed to access that area. If not, pop the fuse out and take it to a hardware store to get a new one. Worked for me. Update (21/04/2020): Sorry for not posting this previously. After trying what I suggested above it only worked for a short time. The true fix was replacing my old panel with a new updated version from the same company sold at Home Depot.