Imo two main issues currently.
1. His finishing is off. He was so extremely clinical and lethal in front of the goal last season. What went in close to the bar last season, he misses closely this season. Might have something to do with his injury but can also be mental. I hope he finds back to his mindset from last season and becomes that lethal Samurai he was last season. He brought so many happy moments to us fans with it.
2. He doesn't come as much in these 1v1 or 2v1 positions as did last season and I don't think this is only his own fault. Surely we are missing Inigo's passing from the back, but that can't be the only reason. Ferran with all his current issues is neither getting as much in these positions as did last season. Something is off in team's ball distribution compared to last season.