Corolla 2009 car is not blowing cold air

Hello. I have corolla 2009 LE. My ac is not blowing cold air for a long time. Only Sometimes it gives perfectly. And most of the times not.

So for that, i have recharged my system at authorized dealership. They found no leaks. And they also put UV die to detect any leaks for future 2 weeks ago.so apparently today, there are no leaks.still tje problem is consistenr. What could be the problem?