PP Install Question

We had Perfect Pass installed and the system works great. We are running off RPM and I wouldn't have it any other way. The one problem we have run into is with the gauge. The first gauge we had worked great but when direct sunlight hit it the display would shut off. The system would stay on and was still working but the display just was off. Anyways I was sent a replacement gauge and said that I would just swap them out. The swap is complete and everything works great but I ran into a problem and I don't know if its a wire I forgot to hook up or we have another bad gauge. But now the backlight doesnt turn on. Is there a wire or something I am missing. All that I could tell there was just the two screws that hold the gauge firmly in place. The old gauge's backlight worked but I can't figure out the new one. Any suggestions......