I'll reply here just to help others out who may be searching for this issue, because I just went through the process before reading this here.
This is the symptom of what appears to be a common problem with Hot Springs spas. The problem is that a relay or a connection on the relay board burns out. Visually nothing may be seen on the front, but when the board is removed, the back is burned underneath a relay(s) where a connection has vaporized.
WARNING - 220 volts is present - know what you are doing or have a competent electrician troubleshoot this for you. The condition is: the heater LED (red) on the board is lit, indicating the control is calling for heat. Checking the voltage on the heater cord terminals shows zero volts.
WARNING - before trying to look at the back of the board, be sure to shut off all power to the spa and CHECK with a reliable instrument that there is no power present. Then you can remove the relay board to inspect the back side. You can also disconnect the heater from the board and test the resistance at this time.
The good news is that the relay board is not too expensive and can be ordered online. Apparently it's an improved version over the one in my 2008 Grandee. Hopefully it will last a little longer...