All other shared mailboxes for other users worked correctly.
All users are running Outlook 2013 32bit with all latest patches at the time of this writing.
The “Mail to keep offline” slider in Office 2016 also affects shared folders. You can set the slider to cache a shorter period of time and thus reduce the size of your offline cache.The “Mail to keep offline” slider does not affect shared folders in Outlook 2013 (and older versions).Navigate to a contact or matter that is not showing in Outlook and check that email sync is enabled by following these steps: 1) Navigate to the missing contact/matter page2) In the about tab, click on "Sync Settings" to expand this option.3) If email sync is set to "No", edit the contact/matter and change it to "Yes".4) Click "Save".5) Click here, to sync now!6) Wait 5-10 minutes for the Outlook Practice Panther folder to update.The user account for the shared mailbox itself should stay in disabled state.
Tip: Before you can use a shared mailbox, the Office 365 admin for your organization has to create it and add you as a member.When someone “owns” a large Shared Mailbox account (e.g., having many large attachments), or has extensive privileges to a Shared Mailbox account, the local online cache (OST file) of their Outlook client becomes too large.The impact on the offline cache file depends on the following: The simplest solution is to turn off "Download shared folders" using the steps below.If you are the “owner” of a Shared Mailbox account, your best solution is to turn off “Download shared folders,” as explained above or upgrade to Outlook 2016.Check out this knowledge base article I found in the West Virginia University knowledge base.You can also use the shared mailbox as a shared team calendar.