Windows Server 2008R2 / 2013 (Shares and Permissions)

I have Windows Server 2013 setup for File Sharing.  I created & Shared the folder.  I set the security and share permissions of the folder with Administrators and a group call Internal Workers.   I do not have access from accessing the share from another computer.  If I added Users to the Security and Share permissions, it works.  WHY???? 

Thank you

Ryan