Is the "flo" message "flashing" back and forth with another message like temperature or time, while the pump buttons and blower are able to work, OR is it solid continuous "flo" message with nothing else working like pump 1 or 2, or the blower?
Trouble shooting tip: with the power to the system on, remove the sensor loom, top-left of center position on the circuit board, and then plug it back in. Let me know what happens.