Just a WAG but I’m thinking either the inlet to the tank or the vent pipe seal has failed. You won’t be able to verify either without dropping the tank. HOT water and Dawn ultra blue May clean the sensors so they will work again, I have a 98% success rate.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.