http://support.microsoft.com/kb/2636318 My personal experience is that sometimes this work around can fix the problem, follow all steps! • Uninstall the app • Turn off WiFi • Reinstall the app • Ensure Auto Discover is set • Enter sign in and password...

Before installing Mobility Service and Autodiscover you need this update http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=11551 When you deploy the Microsoft Lync Server 2010 Mobility Service, users can use supported iPhone, iPad...