Sign in to Microsoft Lync failed because the service is not available of you may not be connected to the Internet.
If you have run into the issue above, the fix is simple. Microsoft has put out a KB article that details the resolution, or you can follow my screen shots below.
Click Advanced at the bottom of the application
Click Manual Configuration
Change Internal Server name to sipdir.online.lync.com:443
Change External Server name to sipdir.online.lync.com:443
Thanks for visiting and reading my posts. I am always looking for more ideas. Please comment or email me with what you would like to see.
Kelsey Epps Office365 MVP