"Did you run a new wire for this 120 V that you wanted? or are you
grounding
out one of the 240V sides?"

He doesn't have to run a new wire. A 240V spa is run with two hots, a
neutral, and a ground. The heater runs on 240V, the pump can be either
240 or 120, and the blower, lights, etc run on 120V.

I would try just hooking up a test lamp without the spa connected to
one leg of the 240V and the neutral. See if that trips the breaker,
which should be GFCI. If it doesn't, then you know the problem is
somewhere in the spa.