We're currently investigating how to enable instant syncing in these situations.
When accepting a shared calendar, you might see an HTTP 500 error. If you see the error more than once, contact Support.
We had to rebuild their outlook profiles to get the shared calendar to work.
Now, even though they can add appointments directly to the calendar from desktop outlook, the other users have to leave their calendar, click on the group in outlook and open the calendar from there, and as soon as they do the group calendar updates in the calendars tab.
If this does not work we will be ditching groups and just creating a sharepoint calendar for their team to use.
If you are making use of shared calendars in Outlook 2016 you may find that not all appointments are showing in the calendar or are disappearing.one suggetion I found online was to disable downloading of shared folders in outlook account.I did this last night and they are going to test today...You will be able to edit the calendar about four hours after accepting the invitation.We're working on fixing this so that you can edit a shared calendar immediately after accepting the invitation.Microsoft first released Outlook for Android and i OS in late January, just over two months ago.The original app was essentially a rebranded version of Acompli, which Microsoft had purchased in December 2014.Select Accept again and Outlook should successfully accept the invitation. Mail for Windows 10 does not prevent you from editing a calendar to which you only have read-access.However, any edits you make will only be local edits—other people who share the calendar will not see your edits.If a tenant doesn't use Office 365 EOP filtering (the MX record points to a non-Office 365 endpoint), instant syncing will not occur.Instead, calendar syncing will only occur a couple of times per day.