Happy player refusing to sign contract?

How many factors influence whether a player will sign a new contract? Heres the deal right, I have a 21 year old wonderkid regen midfielder at a team enjoying Europa League football. He's playing and scoring with some regularity, but with 18 months left on his current contract, he apparently has 'no interest in renewing his contract'.

Now, he does frequently switch between being happy at the club, and having personal problems. Twice I have sent him back to his homeland of Argentina to deal with his personal problems, he's come back delighted, and has still had no interest in signing a new deal. He's also gathered interest from some (not top, but certainly currently higher than myself) European teams which has unsettled him, but he frequently returns to a period of calm where no-one is interested in him, and he is happy to stay.

I have asked him if he could recommend a staff addition, which he couldn't, but appreciated being asked nonetheless. I have asked if he could recommend a potential signing, and he came up with a £10m striker who wouldn't benefit the side one bit. I have since managed to get him to recommend two players from his former club, one of whom will shortly be joining. The other was again, a waste of money.

He has been playing in England for 18 months, and has a further 18 months to run. There are two other Argentines alongside him in the first team, and a further one in the youth team. I offered to increase his contract (£4400 p/w) by a factor of 10, and he declined it.

So I ask, what can I do to convince him that his future lies with me? Is he just that bad at adapting to England that despite his professional displays, he wants to go back to Argentina? (I might add, he has learnt to speak perfect English in his 18 months) Or will he be holding out for a move to a bigger club?

And what should I do now? Sell him, and recoup my losses, or keep a hold in the hope that he will eventually sign a contract?

offer him more money.

I tried. Frankly, when he's on £4400 p/w and turns down £50000 p/w money doesn't seem to be his primary motivation.

ah apologies. i thought you meant you had increased his wage from £x to £4400 which was a tenfold increase. whoops.

sometimes i think players just decide they want to go and there isnt much you can do to stop it. i guess ronaldo last summer would be a similar, if slightly out of sync scenario.