It was reported that the breach related to Grealish's unauthorised absence from training.
The 31-year-old missed Saturday's 2-0 loss at Arsenal in the Premier League due to an illness.
Grealish, who is on a second season-long loan from Manchester City, had started Everton's three Premier League matches prior to their defeat against champions Arsenal.
The 31-year-old has made six appearances for David Moyes's side this term, most recently in their loss against Chelsea on October 17th.
Grealish has been dogged by criticism of his off-pitch behaviour for several years amid reports of nightclub incidents that saw him fall out of favour at City.
After playing a key role in City's treble-winning campaign in 2022-23, Grealish became an increasingly sidelined figure at the Etihad Stadium.
Everton are facing Newcastle for a place in the EFL Cup quarter-finals, with Fleetwood awaiting the winner after their shock victory over Arsenal on Tuesday.