Question HDMI UHD Color no sound

[gediman]

Hello everyone. I have a 4K tv Samsung UN65MU6100 years ago but so far I assembled a 4K pc, the tv is connected via the ARC port to a new Onkyo home theater, so I activate the HDMI UHD Color option and everything is perfect on the pc, but when I go to watching cable channels there is no sound. One option that returns the sound is to disable HDMI UHD Color but if I do the video games are "washed" the blacks are gray. I use a 2.1 certified cable, so that's not the problem, I have the Black Level on the tv set to "Low" which is how blacks look better. I also have the tv and the cable television encoder in the PCM option. What could I do so that I can keep HDMI UHD Color active and have sound on tv channels? I appreciate the help.