Just got my box last week for my bedroom TV that has 4k. Every single night when I come into the bedroom and turn on the TV, there's no sound and have to restart the box every single time.
Every night. Need to replace this now.
you can swap out the set top box to see if the problem is fixed. the audio is delivered without change from production facility where the audio/video was created to your home. It is possible, but unlikely to be the set top box. If you had blue tooth headphones connected to the box and they worked while the TV doesn't, then that would say the TV has the issue. Do you let the set top box go into power save? if so, try turning that off if the swapout does not fix it. might try unplugging the ends of the HDMI cable and inserting feeling for the 'click' of the lock into place on the socket.