So I have user Sam who has full access to user Ruth's inbox and calendar. We have set the permissions in Office 365 and Ruth has also set delegate access to Sam. The issue is when Sam is trying to create a calendar appointment for Ruth it doesn't show up in Ruth's calendar. However, if she uses the webmail portal and creates the appointment it does work. Sam has no other issues with any other users. We have tried removing/stripping all permissions and re-adding them and also tried another laptop with a fresh windows build. Any other options? Help is much appreciated.