The shot clock normally only reset if the shot hits the rim....it doesn't for blocks shots, air balls, balls that his the backboard, but not the rim etc.
it get only reseted when the ball bounces of the rim, i remember a hilarious scene while a team makes a shot in the last second and the ball was betwen backboard and rim. The shooting team had the possesion arrow so get the jump ball, but also the shot clock violation ;)