No airflow from the tip is unusual. If it's a severe blockage at the tip, I might expect to see some blow-back or bubbles in your paint jar, though that's dependent on whether the blockage is inside the tip or outside..
If you're using acrylics, it may be a case of the dreaded "tip dry". Unscrew the tip from the head assembly and swab it out.
Another possibility is a blockage (eg. paint contamination) in your air valve. First, unscrew the tip from the head assembly and press the trigger. If a reasonable volume of air comes out, then it would suggest that the air valve is ok, but if little or no air comes out, it would suggest that the air valve itself is blocked.