Few things you can check. On your Digital thermostat controller, should have a symble display if air conditioner is request to run(House temperature is higher then the setting), if symbol is seen, but compressor not running. Check the disconnect switch beside the compressor out side. If disconnect switch is ON, then check are there any voltage (240Vac 2 phase), if voltage is measured, then check the compressor motor contactor, make sure it is energized, or made sure there is no any dirt on the contactor's contact. Which caused no electrical current connection to the motor