Erik Ten Hag did not handle the issue of Jadon Sancho even if it was the player that made the biggest mistake. There are some comments that a coach shouldn't make against his players. Such comments can reduce the value of the player. He wouldn't have publicized that the reason for dropping the player in the game was because of lack of fitness. And Sancho wouldn't have also countered his coach publicly. This issue would have been handled internally.
Sancho was asked to apologise but he refused. His refusal propelled Erik to ban him from the team. He doesn't train, eat it even stay in the dressing room with the senior team. But the English player has made his decision to move to his former club in January. Manchester United might ask for as much as £40m from Borussia Dortmund.
His refusal to apologise to the manager and club for disrespect shows how arrogance and childish he is, and instead he chose to be watching the matches of united youths and teenagers when they play, instead of training with his teammates and fight for a place in the 1st 11, well i don't think ETH is really to bring him back into the squad even though he'll really need extra players in his squad depth.
I think he'll continue to remain under a ban and away from his teammates and training ground until he's ready to do the needful also it may be that he's no longer interested in playing for united anymore and is comfortable in waiting till the winter windows to be transferred to another team, probably his former team Dortmund cause they'll gladly welcome him back since he's decided to move over there, but if Dortmund is unable to provide the rightful fee demanded by united, then united may seek to do a deal with a more serious club with a better offer.