Emails not appearing in Shared Mailbox for some users

Hello All,

We have recently created a shared mailbox in our Office 365 Enterprise domain and have given seven users access to it.  They have had access to it for a few days now.

While five users are not having any issues, the other two cannot see any emails in the folder.  Here is a breakdown of the clients that they are using:

5 users with no issues:  4 using Outlook 2010, 1 using Outlook 2013

2 users with issues:  both using Outlook 2013

All seven users can see all of the messages when logged into OWA and opening the shared mailbox.  All seven users have Full Access permissions and Send As permissions via a security group.

Thanks for your help!

-tim