In all cases, the user must be in a group that has Attachment Permissions. Given that, there are several ways this can happen:
- An improper upgrade from < 4.0.1, OR
- An improper installation, OR
- In the Lite version, the user was only a member of non-Administrator groups that never had their Sidebar Permissions changed from the default values, but whose permissions of any other type were changed, and then the Lite version was upgraded to the full version, OR
- The user is only a member of groups that were created after all VaultWiki blocks were created and was never explicitly granted Sidebar Permissions, OR
- The user is a member of a group that was explicitly denied all Sidebar Permissions at some point, even if they were later given Sidebar Permissions again, OR
- The user is a member of a group that was given a Never value for any single Sidebar Permission, OR
- The user is a member of a group that was given a Never value for any single permission of a type other than Book, Category, Feed, Redirect, and a Never value for any single Attachment Permission.
There may be other situations, but these are the ones I've been able to rationalize so far. I wanted to make sure that this error was not caused by any missing or invalid data, and that the above edit is all that is needed to correct the issue. Aside from improper install/upgrade above, while some of the cases might suggest behavior inconsistencies that should be addressed, none of the cases suggest any data problems, so no further attention to this issue is needed at this time.