Found system board in low pressure lock out - reset system and waited for time delay cycle. After unit came on checked all electrical components including low pressure switch and refrigerant balance on system. System operates within normal parameters but added 2 oz r410a to adjust subcooling to the target 9 subcooling from 7.5° - cycled unit on and off several times to check operation of unit - replaced customer provided thermostat batteries and waited for unit to cycle on again. Recommend if unit fails this way again to replace outdoor unit board.