Another newbie here, but I searched the site with no matches to my problem.

I just got a used spa that was very recently (1 month ago) refit with SpaGuts controller. When it arrived, i hooked it up to the power straight to be sure everything worked - and it did just fine. Yesterday I hooked up the power properly through a 60amp GFI/breaker box, but now when power is energized, the display blinks with the existing water temp for a few seconds, then the FLO error code comes up. The motors do not even attempt to start but I still get the FLO error. The indicator light above the "Heater On" on the panel blinks. The heater indicator light on the front of the control box does not illuminate. All harness connectors match the wiring diagram and are tight to the motherboard. Here's what I've checked so far:

Triple checked the power, made sure the neutral and ground weren't reversed. The GFI pops when tested like it should, and wiring any different than I did just pops it right away, so I'm sure it is wired properly.

I've checked all the fuses, three slow-blow and one glass one, all have continuity when power off and checked with a DVM.

You can hear the relays click when the pump buttons are cycled.

I've checked power from the input at the breaker box to the control box to the back of each motor and there is power everywhere, power is correct for every connection and motor.

I've tried resetting the flow switch (it's one of those universal looking ones with two contacts on top on either side and a vertical screw for adjustment), turning it three turns each way to see if anything changes, but it doesn't. I reset the power each time I changed it but still nothing. I do not know what or how to use the DVM to check and see if it is functioning or not.

The motors don't hum or anything. There are no visible "reset" buttons on the motors.

All shut-off valves are open.

All air purges have been utilized to the point that water runs out.

The only other thing is one of the air purges was right above one of the motors and it got wet, but it was ventilated and allowed to dry (easy hear in Arizona) for 24 hours before I attempted starting after re-wiring with the GFI.

Any help is greatly appreciated, don't want to just throw parts at it, but the only thing my totally inexperienced mind can think of is somehow the flow switch is bad and I need a new one. Thanks in advance for your help.

Its easy to check the flow switch. Its either on or off. With flow it closes and completes the circuit. Flow can be simulated by shorting its wires together. Other thing to check is the circ pump. Is it running? It should be on any time the heater is energized (it creates the flow the closes the flow switch).