The time request could not be accepted as there is no planned working time in the shift plan.
The error message indicates that the shift plan (planned work schedule) does not include planned working time for this period. Please check the shift plan to ensure that it has been entered correctly and that it has not already expired or not yet started for the period you wish to release.
You can find out more about storing and managing shift plans (target hour plans) in the following instructions: Target hours (shift plans / public holidays)