Steps to reproduce

1. Create multiple directories (Crowd and LDAP). Note: Confluence Internal Directory exist by default
2. If order in User Directories is Crowd (1), LDAP (2), Confluence Internal (3), then neither LDAP or Confluence Internal users can login. Only Crowd users can login.
3. If the order is LDAP (1), Crowd (2), Confluence Internal (3), then only LDAP and Crowd users can login.
4. If the order is LDAP (1), Confluence Internal (2), Crowd (3), then all users can login. Even though all users can login now, if there are duplicate users in Crowd and other directory, the Crowd users password are not used. This is a problem if Crowd is prioritized.

Root cause
This error will occur when Crowd is running versions 2.x <= 2.2.0. It is resolved in Crowd 2.2.2.

Fix
Upgrade Crowd to 2.2.2 or higher.

Workaround
Import the users from other directory to Crowd

This workaround is not recommended, as it does not apply in all cases. Some users (e.g. administrators) must be present in the internal directory to ensure Confluence is accessible when external systems are unavailable, so they cannot be moved to the crowd directory.