The 31-year-old has been absent for Everton's two recent matches against Newcastle United, having been left out of the squad following an unauthorised absence from training.
Moyes had previously indicated that Grealish still had a future at the club, but was unable to give a timescale for his return. Speaking ahead of Friday's game, the Everton manager offered little further detail while confirming the midfielder would again be unavailable.
"No, Jack is not available," Moyes said. "I wouldn't give you the plan but we will be working with Jack again soon."
Asked whether the forthcoming international break could provide an opportunity to resolve the situation, he added: "We just need to wait and see how things go."
Everton have remained guarded about the circumstances surrounding Grealish's absence. The club previously attributed his non-involvement in Monday's 1-0 victory at Newcastle to a lack of fitness, while Moyes declined to elaborate on the issue after the match.
The latest setback comes as Grealish attempts to revive his career after falling out of favour at Manchester City. He joined Everton on loan for a second spell this season, having spent the previous campaign at Goodison Park's successor, where he scored twice in 22 appearances before an injury curtailed his involvement.
The midfielder played an important role in City's Treble-winning campaign in 2022-23 after arriving from Aston Villa for £100 million in 2021, but his opportunities at the Etihad Stadium subsequently diminished.
His current City contract is due to expire at the end of the season, adding another dimension to a difficult period in his career.
Grealish had made six appearances for Everton this season before being left out. Moyes has made clear that a return remains possible, but the manager's latest comments suggest there is still work to be done before the midfielder is considered for selection again.