In the Essentials Dashboard on a Windows Server 2016 sometimes the Server Folders are disappearing and show as ‘missing’. They are actually not missing and still functional if you browse to \\Servername\Sharename as you can see in the screenshot below. The temporary fix for this is to close the Essentials Dashboard and restart the Windows Server Essentials Storage Service. After this you can open the Essentials Dashboard again and all should be fine. Microsoft is aware of this and working on a solution.