PO was not sent via Ariba Network to supplier

Hi,

     After I created a PR, the system mentioned "PO was not sent via Ariba Network to supplier", I find the following failed information:

Response returned with status Code [403] of Type [Forbidden] with message [Error:No relationship with Supplier, name:xxx ANId:AN02000181277. Please contact support with the Error Reference Number: ANERR-20000000000000000014461674 for more details].

[ariba.cxml.service.StatusException: Error:No relationship with Supplier, name:xxx ANId:AN02000181277. Please contact support with the Error Reference Number: ANERR-20000000000000000014461674 for more details]

     Why?