I have a 2003 Grandee model G and I'm not getting any heat.Other than the no-fault heater what could the problem be?

Check the 30 amp breaker.

Check for flow from the circulation pump.

Are either of your lights on the controls flashing?

Some heaters have a reset button on top of the heater under a piece of tape. If it's tripped you will feel a notchy or clicky feeling.

Last but not least, there is a circuit board in the control box that your power wires connect to - check for burning or a burning smell.

the control board shows normal,temp. reads as set,but water is cold and there is no burnt smell from control panel. At present time there is no water in spa,is there a way to check circulation pump without filling spa?

Not really - I've seen them run without a load and as soon as you put it to the water test it won't get started.
If the circ pump was bad the high limit should have tripped and the red or green light would have been flashing.

Fill the spa (put the hose in the gray standpipe), run everything and post again. We will figure it out.