Samsung television apps - no sound with receiver

Apr 4, 2018
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I am attempting to connect a Samsung 7000 series television to a Comcast X1 cable box, and to a Yamaha RX-A870 receiver. Initially I had sound and all was well. I then tried using apps on the television itself for Netflix, and no sound. It was still coming from the tv station that was playing prior to switching to apps/Netflix. I have connected everything using just HDMI cables, and then added an optical cable from cable box to television. I am going from no sound at all to my original predicament. Any input would be greatly appreciated!! Thank you in advance!