The reason your compressor is not running is because of a low pressure sensor on the high side system. When there is not enough coolant in the system, the sensor cuts power to the compressor to prevent damage.....Ironically this doesn't help when you know you don't have enough and are trying to put more in
THE SOLUTION TO THIS PROBLEM IS EXTREMELY SIMPLE
Disconnect the negative battery terminal for 1 minute. This clears the memory in the ECM. Reconnect your battery.
Next, get your coolant/hose and everything ready and hooked up.
Turn on your car and turn the A/C on max. Your compressor will cycle on and you can now recharge your A/C.