Garnacho career at Manchester United seems to be stuck because of conflict with his coach Amorim. His reported high ego and poor relationship with manager have directly caused him to lose his spot on team despite his talent. On top of that even though clubs like Napoli and Chelsea are interested Manchester United high price tag is preventing transfer leaving Garnacho in tough spot as his club price for him is too high for other teams to pay.
It's not just Garnacho several other players have also had issues with Amorim, leading to serious problems for some of them. Some say the players' egotism has led to their problems with the coach, and perhaps there's no harm in that, considering their inconsistent performance. A high asking price will certainly make it difficult for other clubs to sign Garnacho, and the only chance to repair the relationship with the coach is to get playing time this season, even if it's not a priority which Amorim can choose because there are other players who might be his mainstay.