Hello ver bra,
Thank you for posting in Microsoft Community forum.
What did you remove from domain? User or PC?
If you remove PC from domain, you can try to join this PC to domain again.
After that, use the specific domain user account to sign in this PC and access these files and check if it helps.
Where are these files stored? Are these files stored in this PC or in another member server in the domain?
You can try to add this user via permissions under Security tab directly, then sign out and sign in to check if this user can access these files.
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Daisy Zhou