The RS series which feature an optical digital input, can only handle a stereo PCM audio signal.
If you connect it to a device which is transmitting a 5.1 channel signal, the headphones will not reproduce the sound.
It may be that you need to change the settings of your device to output a stereo PCM signal.
We have had some reports of issues with Netflix apps on smart TV's where the default is 5.1.
In this case, once the program is playing, go to the 'Audio and Subtitles' Menu.
Then select the option 'English' rather than 'English 5.1'