Check the Room Thermostat Temperature Setting: Set the thermostat to at least 5 degrees below room temperature.
Check that the Room Thermostat is set to "Cool" not "Off" or "Heat". If the thermostat is not set to "cool" it is simply turning off your A/C.
Check that electricity is on for the equipment. Check all switches and controls, including service switches, including outside by the compressor, inside at the air handler, and fuses or circuit breakers in the electrical panel.