Save the maintenance strategy first

What causes this issue?

You have tried to display the package sequence for a
<GL:preventive_maintenance_strategy>maintenance strategy</>. This is
only possible if you have previously saved your changes to the
<GL:preventive_maintenance_package>maintenance packages</> of this
strategy.

System Response

INCLUDE 'KEINE-FUNKTION' OBJECT DOKU ID TX LANGUAGE EN

How to fix this error?

Save the strategy, or just the strategy packages for this strategy.
Afterwards, call up the function again.

Error message extract from SAP system. Copyright SAP SE.