It doesn't matter if the player plays the ball or not. Entering before the kick is the infraction.
Here's the rule: https://www.thefa.com/football-rules-governance/lawsandrules/laws/football-11-11/law-14---the-penalty-kick
Here's the rule: https://www.thefa.com/football-rules-governance/lawsandrules/laws/football-11-11/law-14---the-penalty-kick