The setup:
Exchange Online user. Has a secondary shared calendar in their account which is shared with other team members with access to put items on it.
The need:
Team members would like to use the calendar from their mobile devices, but it doesn’t show on theirs, only shows on the owner’s mobile.
The fix:
Have the owner un-share it, then Send a sharing invitation in email to re-share it with each team member from the Office Online Calendar interface. Make sure you select the proper permissions for that user.
On your mobile, use the Outlook App(iOS and Android) and open the “I’d like to share my calendar with you” email and then add the shared calendar to your account.
Reference: https://support.office.com/en-us/article/Share-your-calendar-in-Outlook-on-the-web-for-business-7ecef8ae-139c-40d9-bae2-a23977ee58d5?ui=en-US&rs=en-US&ad=US#__toc375064923
PS. Beware of advice to publish your calendar to the web and use the link…I haven’t studied all the ramifications of doing this, and naturally it depends how sensitive your calendar info is, but in general I’d advise against this unless you are sure it’s what you want.
————
If you’re looking for some general guidelines on how to add a calendar from a Shared Mailbox to iOS then refer to this link here: http://help.unc.edu/help/accessing-a-shared-calendar-on-ios/
Note: the steps in the link above will publish your calendar to a direct link which is considered insecure because it can potentially be shared with others outside your organization.
