Issue: On sign-in the error is "the online service is not available"
Solutions: Change the Visual Studio proxy settings in below file.
C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\devenv.exe.config
to
<system.net>
<defaultProxy useDefaultCredentials="true" enabled="true">
<proxy usesystemdefault="True" />
</defaultProxy>
<settings>
<ipv6 enabled="true"/>
</settings>
</system.net>