Package & no longer contained in strategy &

What causes this issue?

The package you entered was removed from the maintenance strategy.

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

System Response

The system can no longer access it.

How to fix this error?

Since there could be calls with the missing maintenance package for
maintenance schedules that refer to this maintenance tasks list, you
should first check in which maintenance plans the task list is used and
create the package again if necessary.

Error message extract from SAP system. Copyright SAP SE.