Lots of things could be wrong.
1. Bad compressor
2. Low charge
3. Faulty clutch
4. clogged evap
5. bad controller
6. Pressure switch
If the compressor is running then that eliminates 1 and 3
If the return line is warm or frosted the it could be 2 or 4
If nothing is working then it could be 5 or 6.
There is also a host of other possibilities.
Unless you know how to troubleshoot an AC system, just forget it, and then a trip to the shop is in order.