Copy ref. object contains inactive MPs that are used for creation of MP

What causes this issue?

You have selected a technical object for which you want to create one or
more new maintenance plans.
However, the displayed list of maintenance plans for the copy reference
objects also contains inactive maintenance plans.

System Response

The system displays two lists of maintenance plans (Maintenance Plans
for Objects, and Maintenance Plans for Copy Reference Object) and their
active status.
The inactive maintenance plans for the copy reference object will also
be used to create the new maintenance plans for the technical object.

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?

Error message extract from SAP system. Copyright SAP SE.