If your hot tub display panel displays an error code, don't necessarily think you should call the service center. You can take care of many errors yourself. The "HFL" error normally indicates a substantial difference between the sensors in your unit, and is normally caused by a water flow issue. Fixing the error codes should only take a few minutes. Before doing anything else to your hot tub, check the circuit breaker and ensure that the unit has power. Error codes may go away when power returns to a unit.
Check the water level in your hot tub. Keep water about 1 inch above all the jets when there is nobody in the hot tub. As people get into the hot tub, the water level will naturally rise.
Ensure that the slide-valves, located inside the access panel, are open. The slide-valve is a "T" shaped panel that is pulled up when "open" and is pushed down when "closed."
Prime the pump to remove air out of the pipes. Loosen the pump union slightly to let any trapped air escape the pipes, and then tighten it back up. Turn the pump on and listen for normal jet sounds.
Clean the hot tub traps and skimmer baskets regularly to keep debris from entering the system.