NBA refs miss fouls sometimes, but they rarely call a foul that wasn't committed. Their policy is only call the foul if you actually see it. College refs see contact and they assume a foul was committed without actually seeing one.

A common area where you will see the difference is shots in the paint when a defender jumps straight up (or is retreating) and has his hands vertical. In the NBA when there is contact they don't call a foul unless they see the hands come down and actually make contact with the offensive player. In college they often call the foul just because of the contact, and even more often if the hands come down, even if there is no foul once the hands come down.

Another area is slap down strips by defenders. In the NBA unless they see contact with the arm/wrist or hear contact, they let it go as a good defensive play. In college it seems like the opposite standard. Unless they clearly see that the defender got it clean, they blow their whistle and assume it was a foul.

Lastly, is charging calls. In the NBA, unless it was a clear charge they will let the play go and tell the defender to get up and play defense. In college they reward soft play and flopping by calling a charge/block seemingly every time a defender hits the floor. Because in their view if there was contact a foul must've been committed.