I believe the no flow comes on for up to 5 minutes during initial start up. if it stays on after that, there may be a flow problem. check at the pool return jet. if there is enough water flow, then the problem could be in the wiring to the generator cell. if there is little flow, then you will have to determine that the pump is pushing water properly. the other common cause of this problem is if the water temperature is out of range or the cell is dirty