Task list selection for order from maintenance plan not allowed

What causes this issue?

You want to allocate a <GL:maintenance_task_list>task list</> to a PM
order that was created from a
<GL:preventive_maintenance_plan>maintenance plan</>. This is not
possible, since a task list has already been allocated in the
maintenance plan. You can no longer change this allocation in the PM
order.

System Response

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

How to fix this error?

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.