Hi Skujovich,
In Office 365, there are 2 kinds of calendar, below is the Exchange Online calendar (Outlook Web App calendar):
Also, we have calendar app which is a list in a SharePoint site:
Both of the two Calendars can be synced to Outlook normally.
What you want to achieve is to sync the SharePoint site calendar list to your Outlook for Mac 2011, is this the case?
Do you have any other browsers to try to sync the calendar?
Is the "Connect to Outlook" button greyed out?
Have you tried connecting your Office 365 Email account to Outlook for Mac 2011? By this way, we can determine if the Exchange Online calendar can be synced to your Outlook for Mac 2011, and this is also a workaround if the calendar list from SharePoint site cannot be synced.
Please let us know your test result, we will follow it up.
Thanks,
Sean Xiao