Purchase order will not reflect changed performance dates

What causes this issue?

You changed the service performance dates of an external service.
However, the purchase order for this service has already been created.

System Response

The system updates the service performance dates in the purchase
requisition, but not in the purchase order.

How to fix this error?

Update the service performance dates in the purchase order manually.

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.