The behaviour of ldap plugin is very strange on OJS 2.4.8-2.
You need first to create a magazine and only then you can add users and define authentication sources for that user.
This is not how people expect to ldap to work, ldap should be a global Authentication method…
Another problem is that OJS does not allow usernames containing dot!!!. Almost all our users have dot in their uid, so this makes ldap on this version of OJS useless.