Sounds like a bad pump.
On my C-320 it's accessed by unscrewing and removing the toilet-paper holder. Make sure the DC panel switch for Water Pressure/Shower Sump Pump is ON; then use the waterproof switch in the head to activate the sump pump. Run it until the sump sounds dry...there is no float switch.
BTW, make sure the through-hull is open.
If the pump cannot work, I'd sponge out the sump rather than let soapy water fester. Access the sump by unscrewing and removing the floorboard at the front of the head door. Next to the non-fastened smaller bilge pump floorboard.