Hot springs Sovereign not heating, No bubbles

[Buickx]

My hot springs sovereign recently stopped heating, has no bubbles coming out of the center drain, and shows a flashing red power light. After doing some research I pulled the filters out, and reset the breakers. About 30 seconds after flipping the heater breaker the red flashing light returned.

I did a bit more research and decided to replaced the thermistors, the circ pump, and tested the heater with my OHM meter (Registered 9.7). But once again upon resetting the breakers, after about 30 seconds, the red light starts blinking again.

I can feel the heat coming off the no fault heater immediately after flipping the breaker, but noticed not a lot of water is being drawn through the outlet tubing of the circ pump. Furthermore, when I place my hand over the standpipe inlet, I can feel that the suction is intermittent (suction for 1 second, stops, suction again for a second or 2 and then stops, so on) I can feel and hear the circ pump humming, and assume its not faulty, as it was bought from the hot springs retailer.

I also opened the inlet and outlets of the circ pump to make sure it was not airlocked, and reattached it. I did the same at the connection to the ozone injector T, which is past the heater.

Also, when I place my hose down the gray standpipe and force water into the system, the heater will remain on.

Everything else seems to work fine (wavemaster pump, light, board, etc.). It’s definitely a flow issue through the heater, but I can’t explain why. The only reasoning, I can come up with is;

A.)    Air is being allowed into the system causing repeated air locks (seems unlikely)

B.)    Circ pump is faulty (but it definitely is trying to draw water through)

C.)    Control board is faulty?

D.)    Pipes are clogged?

[Hot Spring Official]

Sounds like you do not have good flow in your circulation system, so once you turn on the breaker the heater is getting too hot and sending the spa into hi-limit.

You should have at least 3 gallons per minute flowing through the heater.

[Buickx]

14 hours ago, Hot Spring Official said:

Sounds like you do not have good flow in your circulation system, so once you turn on the breaker the heater is getting too hot and sending the spa into hi-limit.

You should have at least 3 gallons per minute flowing through the heater.

Definitely a flow issue. Since I have already changed the circ pump, what could be causing the reduced flow?