[chuckster57]

Who cleaned and flushed it? I’m the odd ball here because my sensors always work properly and every RV I work on has working sensors if I work on it.

I suspect you have toilet paper hung up on the sensors and since they work by moisture/liquid, as soon as there is enough water the paper starts “wicking” the water and.....

Fix: tissue digester and let it sit. I pour it down the toilet and the use the rinser to mix it up good. Watch through the toilet and fill it until the water starts rising into the toilet drain pipe. I leave it for a couple days, and I use the entire bottle.

A 10 pound bag of ice dropped into an empty tank on your way out of the campground can sometimes work too.