I've had the no sound a couple of times before the most recent , but it was always cured by switching off the power to both the TV & box.
I didn't take the mains TV plug out ( it was off but still in standby) this time as it was more difficult to get to due to me rearranging cables in the summer.
So I suspect some glitch or signal is sent to the TV's something like a mute command to the TV HDMI port., and the TV needs a hard restart.
The mute and audio up/down buttons on my TiVo remote don't do anything they never have, but it's not a problem as I use the TV remote for that.
Not sure how long I've had my present TiVo box perhaps 5 years. From the system info
hardware version 4.0
If that helps..
For the volume controls to work on your tivo remote you would need to pair the remote with your TV, you can see how to do this here.
How many times do you have to reboot your box to get the sound working? I've checked this end and can't see any obvious issues with your service.
Have the team ever suggested upgrading your box to one of our V6? If this is something interested in let me know and I can see if this is something we can arrange for you 🙂
Look forward to hearing from you,