I have an SLX250 with the above panel control and indicator panel (same as on the SLX270). My issue is the indicator should show EMPTY/HALF/FULL, but only shows POWER when I turn the key to on. No indication of the level in the holding tank. My question is what is the likely issue? The wiring to the panel is intact and I assume with the POWER indicator on, there is electrical source as required. Can it be a sensor issue on the tank? I haven't tried to check as the access is restricted. Thanks for any input.