Hi,
There are many reasons that your compressor is not coming on. I assume the control is operating and reading correctly. The most common reason for compressor cut-off is the refrigerant level. There are sensors in the system to prevent compressor operation when the system is low on freon. Having a basic A/C service performed at any AC shop will reveal if the system is properly charged. Of coarse if the system is low on charge then a leak dye will need to be installed to pinpoint the actual leakage. Also you can have an electrical problem to cause this which could be the compressor clutch itself, the control head, or a sensor within the system. Diagnostic equipment will be ness to evaluate sensors and electrical commands from the control head. But my first suggestion would be to have a common AC service performed, which should be done every year as maintenance.