Synchronization is not successful

Please confirm the following points.

Calendar is selected in Settings> iOS Calendar Sync.
Calendars is on in Settings App> Privacy> Shift Work Calendar.
The working hours of the shift pattern are set to a time of 0:01 or more.
If it is 0:00, it can not be registered as an event in the calendar, so please set a time longer than 0:01.
In Settings app>Applications>Shift Work Calendar>Calendar you have full access.
In Settings app>Privacy & Security>Calendar, Shift Work Calendar is set to Full Access.

If it is not full access, please set it to full access

iPhone's calendar list is not displayed on the setting screen

Please restart the application and open the setting screen.