I think it's because your team popularity is still not high enough, it depends on how hard you have set the master league difficulty, I'm not talking about the gameplay difficulty but the actual master league difficulty, if you have it set to very hard, players like ronaldo, terry, rooney etc will only come to you when you're the highest ranked team on the game, usually takes 2-3 seasons of winning everything, one way to check is to add them to your scout list, wait a few game weeks and then see what the % number is of them coming to you, if it says 0, then they won't come to you however much you offer, if you get your popularity into the S category then you may stand a better chance, hope this helps