"No Connection" to exchange shared calendar Outlook 2010

Hello experts,

I have an issue with a user connecting to a shared calendar with Outlook 2010 against SBS2011 (Exchange 2010). The issue arises when the user connects to her software based VPN. After she connects the shared calendar shows "No Connection". Emails still work, we can ping the SBS2011 server and her other shared exchange calendar (2 exchange accounts configured, other is Office 365) works fine, the strange thing is another user has the same shared calendar but she can connect to it even after connecting to the VPN. The user that can connect is at a different branch office which is connected via a site to site VPN. In addition the user that cannot connect CAN connect to it when she is at the other branch office. When she is in the same office as the SBS2011 she cannot connect (after she connects her VPN) I think this is a possible DNS issue and I am sure some static entry or setting somewhere should restore the connection but I cannot find it. So I hand this issue over to the experts in hopes of helping me find a resolution to this issue. If you need any further information please let me know.