We hadn't used the spa for a while and last week wneh I went to check the chemical levels, when I put my hand in the water I got a huge electric shock.
I'm guessing it's not grounded properly. I opened the panel too look for something but have no idea what to do.
The service I've had so far from the manufacturer has been slow and unsatisfatory.
Hope someone can help.

Is the spa 110 or 220v, and how old is it?

Who did the wiring, and when?

Why didn't the GFCI trip, or is there no GFCI?

You'll need to determine where the bad ground is- in the spa? At the outlet? At the subpanel?