Error when sending the document to Ariba Network

Hi Experts,

While sending data through PI to Ariba using Ariba Network Adapter , i am getting the below error message.

An error occurred when sending the document to Ariba Network Error: [[Code]: ERR501 [Description]: Unexpected Error [Message]: The url for the outbound is null with request type: OrderRequest] causes a XIAdapterException and can be retried

Can you please suggest what is the reason behind this failure.

Thanks,

Priya Ranjan Saha