Hi RickM11,
Thanks for your update.
According to your reply, the settings in Lync Preferences are correct. Since this feature worked fine on Windows machines, so there is nothing wrong with the O365 account. This issue is related to the configuration of the software on Mac machines.
Firstly, I suggest you install the latest updates to ensure your Lync client been working with O365.
You can download the required updates from here:
http://www.microsoft.com/en-us/download/details.aspx?id=36517
Meanwhile, you can update your Lync client from this article:
Description of the Microsoft Lync for Mac 2011 14.0.4 update.
If the issue persists, I would like to collect some information:
1. Did all Mac users encounter the same issue?
2. Can the calendar be synced in both Outlook client and OWA on the Mac?
Thanks,
Chris Ni