Since upgrading from Outlook 2010 to Outlook 2013, I can no longer access Shared Calendars. When the owner of a Shared Calendar emails me a link to the Shared Calendar, Outlook states that it is "Preparing Calendar for First Use", but then a message pops up that states "We can't complete this because we can't contact the server right now. Please try again later." When I attempt to open a calendar that had been previously shared with me while I was on 2010, although it still appears as a Shared Calendar within Outlook, I receive the same message.
Please note that I can open all Shared Calendars using the Outlook Web App. I also have another PC which still has Office 2010 and I can still view Shared Calendars there.