iTunes movies HD Rental advertised as 5.1 surround, but only plays in stereo
This is a long-term issue for Windows 10.  I've seen problems with all 5.1 sound going back 18 months.  Most posts I've seen say to try this:


Go to your Windows Sounds settings
Under Playback, select Speakers and go to their Properties
Under Enhancements, deselect the Disable all enhancements checkbox
Activate the Enable Speaker Fill checkbox and click Ok


If that doesn't work, try this:


Go to the sound settings
Select your device
Properties =&gt; Advanced tab then select 24bit, 96000Hz from the dropdown