If it is the two button toilet with the front button adding water only.
When it will not close press and then release both the front and back button at the exact same time and it will close. It just takes a quick press of both buttons.
Try power cycling entire coach from main power disconnects and if that doesn’t get it working correct they do sell a very overpriced new controller for more than what a new toilet would cost.
Good luck, hope this helps.
2002 Monaco Windsor 40PKD. Marjorie 2.
2015 Equinox V6 Roadmaster tow setup
2019 ALP Adventurer 24DS for the short trips. April, 2021