No MM purchasing group specified for TM purchasing group &1

What causes this issue?

You attempted to save and post a freight settlement document. However,
the system cannot post the document because some key information is
missing. You specified a purchasing organization for Transportation
Management (TM) in the document, but you have not specified a purchasing
group for the purchase order and service entry sheet creation. The
system needs this information to map to the correct information in MM.
The system cannot create a purchase order and SES.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Contact your system administrator.

Procedure for System Administrators

You must perform one of the following tasks:
Enter the MM purchasing organization for the relevant TM purchasing
group in transaction PPOME -> <LS>Org. Data</> -> <LS>BSD Org. Unit</>.
Enter a purchasing document type, material group, plant, and purchasing
group for the relevant freight settlement document type in Customizing
for Transportation Management under <LS>Settlement</> -> <LS>Freight
Settlement</> -> <LS>Integration for Settlement Posting </>-> <LS>Assign
Purchasing Information for Posting</>.
The system checks the settings in PPOME first, and then checks the
settings in the <ZK>Assign Purchasing Information </>for <LS>Posting</>
Customizing activity.

Error message extract from SAP system. Copyright SAP SE.