Sounds like you need to invest in a set of AC test gauges to check if the system does have pressure. If there is no pressure, then you may need to charge the system enough to do a check to locate the leak. (A cheap set from Harbor Freight will suffice for a non-professional.
If the compressor is leaking around the main shaft, the compressor can be re-sealed by a good AC shop or AC parts supplier. Sometimes it is the hoses that leak. Interestingly,I had to replace the hoses on my Ford car just after the warranty expired!