Greetings
Sundance incorporated a fail safe system into the logic so it will lock itself out if it is not getting enough power to it. Your tub may only be getting 120 volts at the main power hook up terminals. This can be caused by a variety of things including but not limited to a breaker malfunction, a fused disconnect in the main wiring to the hot tub and one fuse has blown or even faulty wiring. If you don't understand electrical respect have an electrician check it out. Good luck!