Windows Server 2012 cannot enable Network Discovery ?
Some MS Security updates or network changes can disable the Network Discovery setting in an effort to secure your server. Unfortunately this can also render many network services unusable.
Traditionally, one is able to turn on file and print sharing and network discovery under: "Control Panel\Network and Internet\Network and Sharing Center\Advanced sharing settings". Unfortunately, under Windows Server variants, one may not be able to change it, the "Save changes" button remains dimmed/unavailable.
If changing it is not available through the Network and Sharing Center, try the "Group Policy Editor (GPO)":
Click "Start", type "gpedit.msc" in shte search box, and press enter.
Navigate to: Computer Policy\Policies\Administrative Templates\Network\Link-Layer Topology Discovery
Click on the setting: "Turn on Mapper I/O (LLTDIO) driver"
After that, you can navigate back and check the setting under "Network and Sharing Center".
Note you may also have to check/enable some services for the network discovery to remain on, see: Network Discovery keeps turning off?