MyBB Community Forums

For some reason, some accounts are able to attach more accounts, others just one.

Also, since a member gave me their password as they weren't able to attach more accounts, I logged in as them, detached the one they had, reattached it, and finally they were able to add unlimited accounts. .... what's that?

Have you already checked the "Maximum attachments per account" setting for the different groups in the user groups management section (MIscellaneous tab) in ACP?