Maintenance plant & planning plant of task list/gen. task list different

What causes this issue?

You have attempted to include a general task list or a task list in the
maintenance plan. However, you are using a planning plant in this
general task list or task list that is assigned to another controlling
area compared to the maintenance planning plant from the maintenance
plan.

System Response

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

How to fix this error?

Assign another general task list or task list to the maintenance plan
or adjust the maintenance planning plant and planning plant for the
general task list or task list.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.