2009.5 pontiac g6 gt coupe

Last year my AC stopped blowing cold air. I live in South Florida and it really sucks, but I didn't have the money to fix it at the time.
Went back home (across the country) for the summer, and got it fixed. Still wasn't performing perfectly, but it was better than before. Air got cooler, but still not cold.

Last week, (back in south florida again) my car almost overheated. Temp gauge went up to 260. I took my car to a shop and they fixed it, there was something wrong with a t-hose that caused my coolant to leak. They fixed the hose, flushed the coolant, and added new coolant.

To my surprise, my ac was working as if it was brand new. It was ice cold.

Three days later, the AC is back to just blowing air. Not cold whatsoever.

What could this possibly be? any ideas?