It's likely that it may need a refill as they do slightly 'leak' over a number years, and it depends on when it was last refilled/serviced. If you are very lucky you might spot a loose connection to the compressor, or the fuse, or an electrical break somewhere else in the system.
If that doesn't cure it, you could have the fault codes checked, or take it to an aircon specialist, or take it to a fiat dealer, but be prepared to spend as much if not more money than the car is worth.