Our home theater system (Pioneer VSX-422) has started to act up while working between our cable box (Samsung SMT-C7200), and tv ( Sony KDL-50R550A). I'm thinking our smart TV is messing with the connection since we didn't have this problem with our older non-smart Tv.
Here is the issue we've been experiencing. Ever since getting our TV, our sound system will work for playing games/dvds, and smart TV functions. It used to work with our cable system for all channels, then progressively stopped playing our English language channels. Now it's stopped playing our normal German language channels entirely. All of our components are run into the sound system via HDMI, before being run via an HDMI out into our TV.
First thing to do is connect the cable box directly to the TV with the same HDMI cable that runs from the Pioneer to the TV and see if the same problem exists. If so then try rebooting the box. Also call the cable company since then the box is at fault.
You can also see if there are any audio settings in the cable box menu.