When trying to move BES users to Exchange 2013 platform through the use of BES Transporter Tool to move the backend BES service and then POA API to add the BES service to the user in the frontend.
Task of the following type failed:
Create BlackBerry account 'firstname.lastname@example.org' (id=123) Last execution output Provisioning request failed. Error in 'BESProvider.addUser'. BESUserAdmin Error. More than one user found: email@example.com,THHSTBESFE01,EMAIL_ADDRESS. Error code: -1. Type: BESProvider.BESAdminException.
Such tasks are designed to be re-entrant, and therefore if the user exists when Parallels attempts to create them, it should see that it has no work to do and complete successfully matching up the user account with the pre-existing one. This is not happening in this case.
The state of migrated accounts is not fully compatible with POA provisioning engine, MPS provider cannot handle returning error code properly, thus does not treat them as "already created", which causes task failure.
The issue will be fixed in future in scope of the request POA-81047, please contact your Account Manager to track down the status of request.