The Barça youngster hasn't fully recovered from his recent injury nor does he have the relevant paperwork yet
Ansu Fati won't be selected by Spain's senior squad or for the U21s. A few minutes before the official squad lists were revealed, Robert Moreno and Luis de la Fuente both decided not to select the Barça youngster.
The main reason is that Ansu doesn't have the relevant paperwork available so he can present his case to FIFA and he's still yet to be given the green light to return to action after his recent injury.