Just a guess but since you admit to not using your a/c since last year, it is possible that some of your R-134a leaked out and the compressor is not coming on. Best way to get your system back in action is to have it recharged at a shop that has an R-134 charging station and can leak check your system. The A/C system should be turned on frequently, event in winter, to keep the compressors seals lubricated and prevent this sort of thing from happening.