All the tank levels or just the black water? If all I would check for a fuse. If just black I would flush tank 2 or 3 times to make sure all the sensors are clean.
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Ray & Diane
2005 Winnebago Vectra 36RD
Honda CRV
I would first check if any wires came loose behind the panel. 4 screws (each corner) seems pretty easy. If no loose wires then I'd check the 12 volt breakers.
When I took the levels indicator panel out of mine, there was a circuit board trace too close to the bottom edge of the board, and it shorted out by touching the metal panel it is screwed to.. repair was to solder in a replacement wire parallel to the trace that burned. Hope that's not yours too, but maybe?
There's always the possibility that it noticed just how useful it is and decided to give up. OK - some of them have a fuse on the circuit board. Most of them have power available all the time on a bus bar on the circuit board. Pressing one of the buttons supplies power to the circuit chosen, and sometimes causes the board to flex, eventually breaking a land. All it takes is a hairline crack.
Check the board carefully after determining that you DO have 12v at the bus.