Need a bit more info first. Is there a 50 amp breaker in your main panel that feeds a small panel on your spa that has a 30 amp GFCI and a 20 amp breaker in it? Or is the main breaker in your panel that feeds the spa a GFCI?
If the 30 amp GFCI is tripping then this indicates a problem with the tub. First thing you should do is open the breaker for this circuit and remove the LOAD wires from the GFCI. Then close the breaker and try to reset the GFCI. If it resets then the problem is with the spa, if it doesn't reset then you need to replace the GFCI with a new one.
If it resets then I would lable all the connectors that attach to your spa pack housing, then disconnect them all and apply power. If no trip then shut off the power and one by one hook them up to find which item is causing the trip. I had an ozonator that would do this, your's may be something else.
Here's a link that'll help in the details. http://www.hottubessentials.com/troubleshooting_tripping_GFCI.htm
Let us know what you find.