You are trying to move a mailbox from Exchange Online to Exchange OnPrem, and you get this error message:
“MigrationPermanentException: Cannot find a recipient that has mailbox GUID <GUID>”
MSKB Article explains why it happens and how to solve it. It involves note down the mailbox GUID from Exchange Online and modifying the mailbox GUID in OnPrem to the Remote Malibox. That is two different PowerShell sessions (one to Exchange online and another one to Exchagne OnPrem).
If you use my script to connect both Exchange Environments on the same PowerShell Window, you can fix the GUID in single command.
So here it is:
Set-OPRemoteMailbox -Identity <MailboxName> -ExchangeGuid (Get-EOMailbox -Identity <MailboxName>).ExchangeGuid.guid