The still of the 'offside' is irrelevant. The ball is played by the 2nd Norwich player up (from the bottom of the area) who isn't in an offside position.
'Twas an Premier League game at Crystal Palace (vs. West Ham). The one where Dwight Gayle was also sent off for two cautions. I think it was Gayle who also encroached at the penalty. The fact that Gayle was almost in more advanced position than the kicker and blocking Clattenburg's view of the kick probably swayed his decision.Clattenburg has done it this season, can't remember the competition.