Yes, its the changing responsibilities for him in the team.
Before he was our main goalscorer and playing next to Mandzukic, who is great at setting you and playing with his back to goal. Mandzukic is like the perfect partner for a SS to score. When we played Dybala-Morata it never worked.
Now with Higuain, Dybala has to be the provider first and create more for the team. Specially earlier in the season when our midfield was a train wreck and Dybala had to drop way back to create. He didn't score much in that period, but he was basically our entire game. It was dire to watch our play when he was out.
For how much he "looks" like a playmaker, Dybala has always been the goal scoring CF at Palermo (playing in front of Franco Vazquez) and in his first season here. So now he has adapted to a new role and it takes some time. He is playing great, just doing different things.