2024 Sandpiper 4002FB grey tank issue

Hi everyone, I have a new leftover Forest River Sandpiper 4002FB. It has 2 grey tanks, 2 black tanks and a galley tank. In the front compartment where the water comes in is the valve for the black and galley drain, in the rear on left side behind tires is a black water for rear bathroom and a grey water drain. My grey water #1 is showing full on the gauge but I don’t see a drain for it and camping world has not been any help. I am traveling in Texas and it’s supposed to get down to 13 one night this next week and I’m not sure if tanks are all drained or one is full. Just wondering if anyone else has this model. Hoping it’s just a sensor. Thanks