I came across this issue today when migrating a users to SfBO.
Getting the following error when migrating a users from Lync 2013 to SfBO using PowerShell.
Use the following command to force the user data up into SfBO.
Move-CsUser -Identity <UPN> -Target sipfed.online.lync.com -Credential $creds -HostedMigrationOverrideURL https://admin0a.online.lync.com/HostedMigration/hostedmigrationservice.svc -Force
Remember when using the -Force switch it will move the user up to SfBO but you will loose local contacts and also any meetings which the user has created.
To mitigate this, export the users data by using the following command.
Export-CsUserData -PoolFQDN "<FE Pool>" -UserFilter "<UPN>" -FileName C:\<FileName>.zip
You can then import the user specific configuration by using this command.
Import-CsUserData -PoolFqdn “<FE Pool>” -UserFilter "<UPN>" -FileName “C:\<FileName>.zip”