Offboarding error

Hi all,

I am trying to move back a mailbox that was recently migrated to Exchange Online.  I am running the following command from Exchange Online Powershell:

New-MoveRequest -Identity user1@mydomain.com -Remote -RemoteHostName hybrid1.mydomain.com -TargetDeliveryDomain 'mytenant.mail.onmicrosoft.com' -RemoteCredential $credentials

Error: Target user 'User1' already has a primary mailbox.

I have also tried to initiate the new move request from the pn premise server:

New-MoveRequest -Identityuser1@mydomain.com -remote -RemoteTargetDatabase MyDB1 -RemoteHostNamehybrid1.mydomain.com -TargetDeliveryDomain 'mydomain.com' -RemoteCredential $credentials

Error: Parameter set cannot be resolved using the specified named parameters.

Any ideas what I am doing wrong?

Thanks for all the help,

Mike