2013 35qsik tank question

[mgg123]

I have had this since February, spent 20 or so nights in it, after camping I drain tanks normally go inside and check LED indicators they always show empty. Just came back from a 2 nighter emptied tanks at park as I normally do , the LED indicators still show two tanks 1/3 full. I have tried to empty more again here at home and nothing comes out but the LED still show two tanks 1/3 full. Any ideas what may be the problem?

[Ford Idaho]

Black tank?
TP covering the sensor.
Gray tank?
Oil or grease covering the sensor.

[wyo700]

If both tanks are doing it then more than likely the black tank has paper stuck on one off the sensors and the grey tank possibly has food of some sort stuck to a sensor. I would fill tanks go for a drive to slosh around water and then dump tanks that should do it.

[mgg123]

They are both grey I will try filling and driving thanks