Symptoms

When upgrading Confluence 2.6.x or below to a later version eg. 3.1.x or later, Confluence reports a 'Not Permitted' error when trying to login.

Cause

LDAP Group membership unfortunately is not retained when using OSUser management and LDAP. This is a known problem that has been filed in CONF-10654.

Workaround

Refer to Migrate to LDAP User Management From OsUser.