When running a report some users experience some fields not returning data, where as another user may see the data.
This can occur when a user does not meet the ACL requirements to read the field or table.
To check what ACL might be causing the issue you can run a security rules debug as an admin user impersonating the affected user.
Note: Another way to check the users access is try accessing the list view of the table and add the field that is trying to be viewed. The table list view is another place the Debug can be used to check.