SSO Authenticator doesn't work for new created crowd users

We have a Jira (Version 6.2.6) and Confluence instance which are both using a Crowd directory (Crowd version 2.7.1). We are using the Seraph SSO Authenticator to authenticate our users.

The bug:
If we add a new user to Crowd (new employee), it is not possible for this user to authenticate/log in at Jira or Confluence. We have to do a manual synchronization from each (Jira and Confluence) instance with Crowd. With the standard authenticator implementation no manual synchronization is needed, cause the new user will be added automatically. The Seraph SSO Authenticator should also add new users from Crowd in the local Jira/Confluence CrowdCache automatically like the standard authenticator does.

Step by step:
1. Create a new user in Crowd
2. Change the authenticator for jira to SSOSeraphAuthenticator (serap-conig.xml)
3. Open Jira and try to login with the new created user
The authentication fails.

After a manual synchronization with Crowd, the authentication at Jira works fine.