When you install vSphere Client 5.x on Windows 10 computer. You may see “Enable .net 3.5 failed” message. And when you try to enable .Net 3.5 on Windows 10 manually, it shows error code 0x800f081f.

This issue occures on internet blocked or policy restricted computer. The only way to avoid that is use command line to specific .Net local path and force install it.

  1. Mount the Windows 10 ISO to your computer as a new drive.
  2. Copy the path of “xxx:\sources\sxs“.
  3. Run the following command.
    dism /online /enable-feature /featurename:netfx3 /all /limitaccess /source:xxx:\sources\sxs