Hi , On Feb 5th 2019 I update the software(Android) , since then I lost sound on the apps such YouTube, Netflix etc… But,...

aah fixed it myself. usb(for wireless headphone) was connected to my tv, even though i didn’t switched on my headphone for years causing the issue. Maybe in latest software they have added feature(or bug) to send sound to headphone even when you do sound test. Anyway, solution is to disconnect everything… means EVERYTHING and see else repair your TV.