The decision to sell player would be made by more than one or two people in a club. Just because having a good relationship with the president, doesn't make everything will go smoothly. Maybe personally Perez giving an 'OK' signal, but maybe others said no because it is Mourinho, who knows. Mourinho departure usually leaving a bad taste to every single cells in the club, maybe there are some (stakeholders) who still having some grudge against him.