Which cell are you using (T3, T9, or T15)? If the main panel isn’t set correctly with the particular cell being used you can get wonky readings.

Also, check where the cell and flow switch connect to the panel and make sure the connections are clean.

Concerning the flow switch, make sure when installed the arrows on it match the water flow direction.

When I started mine up last spring I got the solid no flow light. I made sure the connections were clean, and after running a little while it started working fine and has been fine since (I thought I might need a new switch).