Obviously, it goes without saying that both TV & ONN volume has to be up.
Here’s another idea: I had the same problem with one of the earlier ONN boxes. Seems like every once in awhile the volume on the box would reset. Not exactly sure whether it was related to an update, or not.
Nothing I tried worked, so started a search. Came across a post that recommended to use a voice command to restore volume.
The suggestion was to press the microphone button, then say “Hey Google, maximum volume.” Believe it or not, this worked for me.
I had the same issue with an ONN box and another box an issue with the box constantly resetting. The cable connector “on the box” is weak and tends to loosen up. Just from walking across the room and the slightest vibration caused both these issues. I used a small piece of plastic to wedge the connection, to keep it from happening. Then, when I had time, I took both ONN boxes apart and put in a new connectors.
Keep on keepin on !!!
David
I just kind of realized I’m now 100% ONN boxes (both 4ks and Pros). Naturally retired my more expensive and more “powerful” MeCools and Cubes. Never had any problem with the ONNs and they are seamless in operation. All I ever have to do is clear cache every couple of days. They really are kind of a revelation. But really appreciate these “fixes” in case something comes up. Why do I think nothing will come up? Did I say revelation?
now that procedure would make a good video, and be just dangerous enough for me to “FUBR” my box… 
