BTW, yep, the "high limit" message notifies you that the tub has reached an upper control limit for operation and automatically shuts off the heating mechanism.
Sometimes this can be caused by a heater or temperature probe malfunction where for some reason the heat just keeps running and running and running...
Resetting usually takes care of it, BUT, if the spa temperature is STILL above the HL setting (I think 115?) it will STILL display the error.
Good luck...
Drewski