No maintenance plan simulation possible

What causes this issue?

You tried to go to the maintenance plan simulation graphic within the
maintenance scheduling overview. You reached the maintenance planning
overview using the menus <LS>Change, display maintenance plan</> or
<LS>Schedule</>.

System Response

Changes to the <DS:GLOS.maintenance_plan>maintenance plan</> are not
allowed if you have called up the maintenance scheduling overview using
the above menu paths. The maintenance plan is blocked. You can only
display it.
If you use a variant that enables an immediate jump to the maintenance
plan simulation, then the system switches to the maintenance item
overview.

How to fix this error?

If you want to make changes to the status or schedule of a maintenance
plan, you have the following options:

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

Call up <LS>Change maintenance plan</> or <LS>Schedule maintenance plan
</>.
Call up the maintenance scheduling overview <ZH>directly</> and not
from another menu path.

Error message extract from SAP system. Copyright SAP SE.