Release not possible as MaintPlan already released, called or skipped

What causes this issue?

You have tried to release a <DS:GLOS.maintenance_call>maintenance
call</>.

System Response

The system has recognised that this is not possible because the
maintenance plan due for this date has already been:

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

Released
Called or
Skipped

Error message extract from SAP system. Copyright SAP SE.