Purchase Order creation not generating n Database

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Hi All

When one users tries to create a Purchase Order, the document number is automatically created and displayed, but the button "Create" still active.

The record has not been created in the database.

When the screen is closed, the entry is lost.

Does anyone know what kind of setting possibly causing this error?

The user access rights for the user around the PO looks good. 

Thank you for your assistance.