Hi, I am trying to troubleshoot my spa not working.

Here is some background. This is a 1989 down east spa. I got the tub used. It was in full working order when I picked it up, other than the heater did not work. I purchased a new heater (coil type, with a plate and two terminals) and installed it. I than wired up a spa dissconnect box. The unit is 4 wire 220v, and the spa is rated at 40amps. I am good with electronics, mostly on cars, so some things I am still learning with home electrical. I have power at the tub now, but nothing is come on or working. Ok just to clarify I have two hot wires a ground and a neutral. All are hooked up correctly. Here is were I am not sure. I have two hot wires and was checking for voltage. One lead on the ground, the other on the hot wire terminal. I checked line one and got a voltage reading. I checked line two, and the gfi popped. Two things happened, I heard the conctactor in the box "trip", and I noticed the gfi popped in the discconect box. Whats the deal with this? This should not happen correct? The tub has its own gfi as well. Are you suppose to have two gfi's in this type of setup? I.e. a gfi dissconnect box, and a gfi in the tub panel? The gfi only trips in this situation only, other wise it does not trip. Also when poking around, I noticed that there is power to one side of the contactor, but nothing out. There also appears to be a capacitor as well that has power going to several of its terminals, but not to all. Not really sure whats what here. I did dissconnect all the heater wires to see if that fixed the issue, but it did not. Been poking around for hours. Frustrated now. Would love some help!

Ok problem solved. Minor issue with the orignial wiring in the home. Works great now