Have a Goodman heat pump about 3 years old. Currently have thermostat set on 72 but will not pull inside temp down below 78. From what I have read, there are no reset buttons on these units. Do have 2 circuit breaker boxes outside at unit. Any suggestions??

Is the outside condenser unit running?
Does system have a clean filter?
Have you seen any sigh of freeze up? Either on lines (copper) as they leave the condenser or on the lines as they go into the airhandler at the evaporater coil.