Vendor &1: Mandatory partner role &2 is missing for purchasing org. &3

Similar to CMD_API100

What causes this issue?

The system checks whether all mandatory partner roles exist for each
purchasing organization.

System Response

The system terminates processing if the check fails.

How to fix this error?

You must transfer the mandatory partner roles for each purchasing
organization during creation. You cannot delete mandatory partner roles
when making changes.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.