Once you have migrated all Domain Controllers from Windows Server 2008R2 to Windows Server 2016, if you want to raise the forest and domain functional levels from Server 2008R2 to higher version, you can only able see “Windows Server 2012/R2” and “Windows Server”? what would be “Windows Server” and why its not showing any windows version
Even after you raise the DFL and FFL to “Windows Server 2012 R2” successfully, still there is option to raise further to “Windows Server” and it should be Windows Server 2016, why it s not showing correctly and can I raise again to Windows Server to make the DFL and FFL to “Windows Server 2016” to get the new Windows server 2016 features
Also Read: Active Directory 2016 New Features
Did you tried directly on one of the Windows server 2016 Domain Controllers, because we had a similar problem where we are using the Windows 10 admin tools to do this, on the new Windows server 2016 DC, we are able to see the “Windows 2016” on both the Forest and Domain functional levels.
This issue might be with the display string of Forest and Domain functional levels which is not updated and please do update all latest cumulative updates to all the Domain Controllers and tool servers where you are checking this and check again
Hope this will help you to fix the issue