I normally use Power Apps through Power BI to view and submit data to my Sharepoint Lists and in the past 2 days the Apps have been showing the following error in some (not every) users.

"You don’t have permission to view this data. Server Response: Error from token exchange: User …. not allowed to access connection …."
I already tried everything related to "Sharepoint Access" but nothing works. The problem dissaper for some hours and now is again there.
Is kind of urgent. Thank you.
@Anonymous