DO you have a RED Light (Black Tank FULL Indication) on panel?
Full Black Tank shuts down DC to controller (Item J)
If you have access to black tank....disconnect high tank level sensing wire (For toilet...NOT for tank Monitor Panel) Could be Yellow Wire
IF NO RED light on control panel......
could be bad control panel or control module (Item B or C)
http://productimageserver.com/litera...al/56503OM.pdf