monitor panel black tank display

I know most don't care if there monitor panel readings work or note. My monitor panel appears to work just fine for the two gray water tanks, fresh water tank, water heater and water pump. The only issue is the black water lights are all kit. I cleaned the black tank pretty well and then installed NEW Horst Miracle Probes; all the wires from the probes look fine. All the lights on the monitor panel are still lit. I am not sure how this system works but the probes provide ground I am sure when water reaches them and since there is no water reaching them, where could the ground be occurring? The probe wires all go to a red thing and I suspect the hot wire is just inside the monitor.

Any help on how to trouble shoot this issue would be appreciated! TIA wg