I have a unit that can either heat or cool my pool water. The problem is the unit will only turn on in the cool mode setting. Most of the time the unit will not turn on when I am trying to heat either the spa only or the spa and pool together. There is a "switch ritual" that works sometimes where I shut the heater power down (circuit breaker) in the control panel, turn the heater unit switch to heat, turn the heat knob all the way up and then switching the circuit breaker back on. Sometimes this works but most of the time is does not.

Does anybody have an idea what the problem is? I thank you for your help.