Did you get this issue fixed as I'm having the same exact problem with my TV and it's also around 6 months old.
I lost sound on my hisense tv and now I can't control it from my remote or the tv itself. It still has a picture but no sound. I unplugged it from from the wall and can turn it back on but after that I can't do anything. Is this a common problem and if so is it easily fixed?