You will receive the following message when logging in to the Lync for MAC client: 'Sign in to Microsoft Lync failed because the service is not available or you may not be Connected to the Internet'.
If you are using a self-signed certificate from the in-house local CA Certificate on the Lync Front End server, it is likely that you have to install the CA root certificate on the MAC client (because you haven't made the MAC client a member of the domain). The update will also bring some New functionality to the stage as described in Office Blogs. If you have upgraded to Yosemite, you need to update Your Lync for Mac with Update 3007876 for Lync for Mac 2011 - KB3007876 In order to connect to the Lync Server 2013, you need to update your Lync for Mac with Update for Lync for Mac 2011 - KB2909662 Here are some basic troubleshooting steps: I have experienced some problems with connections to Lync Server 2013 from the Mac client.
