Failed to set license for user - 'user@domain.com': 'The creator of this fault did not specify a Reason.'. (4313848)

In a hybrid environment the MAgE (Migration Agent for Exchange) is failing to set a license for the user with the error message below:

Error Quest.MigrationManager.Exchange.O365UserProvisioning.O365UserLicenseException: Failed to set license for user - 'user@domain.com': 'The creator of this fault did not specify a Reason.'.

The MAgE is trying to set the license via PowerShell but Office 365 is returning the failed error.

This can be caused by different issues.

1.) The service account being used does not have an E3 license itself.
2.) This can also be caused by conflicting licenses already assigned to the Office 365 user.
3.) One other possibility, is that Office 365 Licensing & Provisioning process is taking a while to assign the license to the object.

While you can go into the Office 365 Portal and manually assign the license, this will break mail redirection.  

1.)  Verify that the service account being used has been assigned a license itself.  This will allow the service account being used by the MAgE to assign licenses for the mailboxes it processes.

2.) Look at the problematic user in the Office 365 Portal and make sure that it doesn't have any already assigned licenses.  If there are already licenses assign but no mailbox created.   Remove the licenses from the user through the portal and let the MAgE agent assign the new license.

3.) See this KB for an explanation regarding the delay in Office 365 Licensing & Provisioning delays.

https://support.quest.com/migration-manager-for-exchange/kb/146322