Hi...
Our spa has worked fine for years... now, over the winter, the heat stopped. I flipped of the breakers and now all I get is a red flashing light. I called Hot Spring and they said it is a flow problem. They told me to take the 3 filters out and see if it worked. It didn't! Be it known that when I opened the "panel" the "heater reset" button was tripped. I reset it... thought I had found the problem... But to no avial... flipped the breaker and a flashing red light... Thoughts??? I'm hearing about a possible air pocket... but I tell ya... I don't get any flow... when I push the buttons it just looks at me.... Also, I should tell you that when I flip the breakers on... the lights go on for approximately 5 seconds and then I get the flashing red one....HELP

You should have a small circulation pump on this thing. You need to check this small pump out completely to be sure that it is:

Running
Not clogged up

This may require you to disconnect power, disconnect the hoses to the circulation pump and see what you find. It could be something as small as a piece of garbage stuck in the suction side, or a dead pump altogether.