Hi Knoodle,
Sorry for the inconvenience caused by the issue. However, currently it’s not feasible to access the shared calendar on mobile devices via the ActiveSync feature. But you can try to access shared calendars via the App. The App is designed for iOS devices, specifically iPhone and iPad. It is available only for the customers using the latest release Office 365.
For more detailed information about installation/setup and requirements, please refer to the articles:
1. OWA for iPhone and OWA for iPad
2. OWA for iPhone
Moreover, have you tried to contact our Microsoft community Outlook for Mac support? If not, then I’d like to involve our dedicated Outlook for Mac support team in solving the issue for you, because the engineers there are more professional in Outlook for Mac related issues . Please post your question in this forum and our engineers there will be glad to assist you.
Thanks for your patience and understanding.
Best regards,
Shyamal