Users cannot edit attachments?

[RedGTiVR6]

I'm having an issue where users who have uploaded attachments cannot delete and reupload attachments to the same post.

Essentially, they want to upload a new version of the attachment (new release), but they cannot. They are given a permission error:

do not have permission to access this page. This could be due to one of several reasons:

Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

Any ideas?

I've checked User Group permissions, Forum permissions, attachment