Service performance dates changed but purchase order already exists

What causes this issue?

You rescheduled maintenance order operation &VAR1& and the system
automatically recalculated the operation start and end date. This change
also affects the service performance dates of external services procured
for this operation. However, the purchase order for these services has
already been created and is not automatically updated by the system.

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.