There are some recent updates to Server 2012 and R2 that have been causing lots of people issues in deploying Windows 10 to client computers as an upgrade.  The most common issue is a loss of connectivity from the client computers to the local WSUS deployed and a no longer functioning admin interface for WSUS.  Microsoft in their great wisdom has outlined the steps to resolve this, but didn’t make it particularly obvious prior to install.  You can find the steps at the following link.

Pretty simple over all – you launch an elevated command prompt, run this line:

"C:\Program Files\Update Services\Tools\wsusutil.exe" postinstall /servicing

Following that, launch the local server manager dashboard and hit the 'add roles and features'.  Under the add features portion, open up the .net framework section and add 'HTTP activation' to your server.  This won't require a reboot, so follow though by hitting next and so on until it starts the task.  Once completed, you can restart the server or simply restart the WSUS service.  Like magic, you should be back in business.

If you have SSL enabled on your WSUS server, you should review the above link for further details.