MU wants de jong but de jong didn't want MU. The club can't force the player to accept its offer or it will be giving a very bad impact to the club. You must also aware if de jong has said that so many times if he will prefer an offer from another team rather than MU.
I think that chelsea didn't even want de jong and it's still a rumour that is spreading to the supporters. The competitions to get the new players are very strict these days.
It seems like so many rumours are just rumour5.
My guess, De Jong didn't want to give up the chance to play in the UCL. After all, nothing can be promised from MU, not UCL, not even EPL Champions. A player who wants trophies and better competition, will not go to Manchester United at least for this season. Because, the opportunities they have at current club are better than MU. Perhaps, Manchester United will find it easier to bring in players who do not play in the UCL this season, thus nothing has to be sacrificed when moving from their current club to MU.
I don't know for some reason it seems like Manchester United is very adamant about getting De Jong even though De Jong has said that if he still wants to be stay in Barcelona, although Barcelona and De Jong have their own unresolved problems (salary) but it seems Manchester united is just wasting time to keep waiting and seducing De Jong to move, indeed there has been a close relationship between De Jong and Ten Hag so far but for now it seems that there is nothing so special about Manchester United that makes De Jong interested in joining, I agree with @masulum, because instead of wasting time and energy just to persuade De Jong, wouldn't it be better for manchester united to look for another quality midfielder, if manchester united continued to spend time just chasing De Jong, of course, when the transfer market closed they would not be able to get anyone.