1991 Audi 200 Turbo A/C failure

[JCAudi200]

Hello all. I recently had my A/C system converted over for R134A and unfortunately, it now will not produce any cold air. I have had the vehicle looked at three times and subsequently purgered and recharged accordingly to no avail. Is there anything that my mechanic may be overlooking as no leaks have been identified nor any problems with the compressor. Any assistance is appreciated.