Is the heat pump on or off? Check the display, Check the circuit breaker, if that is on (up) push it down and then up again. If that’s not it, check to see if there are any other isolator switches near the heat pump, if all isolator switches are on and the unit is still off there may be a problem with the wiring or electrical supply, either in the breaker box or to the heat pump.
Important: Use caution when attempting to resolve an electrical issue, especially around water. If you do find an electrical issue, you’re not comfortable addressing yourself, don’t hesitate to call a professional.