It was the unsuccessful 2 pt try by Tampa Bay. Receiver was playing the ball and the defender was not. No call - I agree with the no call. If the receiver had fought hard to get to the ball I think PI is called - since the defender isn't playing the ball. "Position" defense isn't necessarily legal (I've been in a bunch of arguments about this).
Too many times over the years a UCLA receiver failed to fight to get to the ball, and allowed himself to get run off the ball. No PI is called even though the defender is not looking back at the ball. If he had tried hard to get to the ball and (not looking back) defender gets in the way - it's PI.