This from the Aqua Cal tech area:
Ask the h/o if he has a variable speed pump. if so, ask if the flow rate is below 30GPM (or 20 GPM for a T055/T075). If they do not know the flow rate, they can ask the installer or if they have a pool service.
Check the skimmer and pool pump baskets, that they’re clean.
Check and make sure all the valves are in the correct position-if they have a bypass valve leading into the heat pump, want to make sure it’s open.
And check the water level in the pool, should be at least halfway up the skimmer.
Also, make sure the pool pump is on-sometimes the h/o forgets that the unit needs the pool pump on to run the heater….
If everything checks out for the trouble shooting, then its advised to set up a svc call.