It is a common problem. The senors get clogged or covered with TP and become useless. I've had this problem and tried dumping Ice in the tank and going for a drive. Worked a bit. Dumped lots of cleaners into the tank. Worked a bit.
Finally I installed tank flusher. After you dump you connect the flusher and it sprays and cleans the contacts as well as the tank.
https://www.amazon.ca/dp/B000BUU5TU/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=2E8YK0LMG31U2&coliid=I1WI01YBZJO3G1&psc=1
The less you plan the more options you have.
Currently with a 26' Forest River Class "C"
Ex Navy Diver
Ex Archaeologist
Ex Museologist
Actively retired