Error when creating document flow for delivery

Hi,

I would like to post the GR for Inbound delivery. I receive an error the TO is not confirmed. I have tried to confirm the tranfer order and I receive the "error when creating document flow for delivery . In order to avoid inconsistencies the goods movement posting was cancelled." It seems like the document already exist.

How can I do to confirm the TO and post the GR.

Thanks

Dede