Generate period work schedule &1 for &2 in &3

What causes this issue?

The work schedule &V1& has not yet been generated for the employee
subgroup grouping/public holiday calendar/personnel subarea grouping
&V2& for &V3&.
You have performed an action for which the SAP System requires
information on the employee's valid work schedule.
Employee work schedules are created for a specific period of time. The
work schedule requested does not exist for the time period specified
here.

System Response

The SAP System can generate the work schedule internally to perform
this task. If you want the system to do this, activate the
<ls>Automatically generate</> field in the work schedule rule &V2&/&V1&
.

How to fix this error?

The work schedule is only generated for this task. For the work
schedule to be used for other tasks without wasting performance time,
generate the work schedule using <DS:TRAN.PT01>Create Monthly Work
Schedule</>.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.