Cannot install .net 3.5 as feature on Windows Server 2012 R2

We are failing from multiple methods to get this installed. We've used the Server Manager, PowerShell and DSIM from an elevated command prompt.

We have the 2012R2 ISO mounted as X: and an alternative path as X:\Sources\sxs

Here are the command lines we've used without success:

C:\>DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:X:\sources\sxs

Deployment Image Servicing and Management tool
Version: 6.3.9600.17031

Image Version: 6.3.9600.17031

Enabling feature(s)
[===========================66.2%======                    ]

Error: 0x800f081f

The source files could not be found.
Use the "Source" option to specify the location of the files that are required t
o restore the feature. For more information on specifying a source location, see
 http://go.microsoft.com/fwlink/?LinkId=243077.

The DISM log file can be found at C:\Windows\Logs\DISM\dism.log

Powershell:
PS C:\> Install-WindowsFeature NET-Framework-Core –Source X:\Sources\sxs
Install-WindowsFeature : The request to add or remove features on the specified server failed.
Installation of one or more roles, role services, or features failed.
The source files could not be downloaded.
Use the "source" option to specify the location of the files that are required to restore the feature. For more
information on specifying a source location, see http://go.microsoft.com/fwlink/?LinkId=243077. Error: 0x800f0906
At line:1 char:1
+ Install-WindowsFeature NET-Framework-Core –Source X:\Sources\sxs
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (@{Vhd=; Credent...Name=localhost}:PSObject) [Install-WindowsFeature],
    Exception
    + FullyQualifiedErrorId : DISMAPI_Error__Cbs_Download_Failure,Microsoft.Windows.ServerManager.Commands.AddWindowsF
   eatureCommand

Success Restart Needed Exit Code      Feature Result
------- -------------- ---------      --------------
False   No             Failed         {}
dism.zip