Hmmm. :-/ I cannot figure this out! I don't have a Win10 computer so I can't mess around and look through settings etc. except in Chrome, where I don't see anything that looks relevant. I'm guessing it's some kind of bug in Chrome - maybe with the latest update, since 87.0.4280.88 appears to be the latest version (just released in the past week or so). That doesn't help you fix it, though.
If no one else comes along with an idea, things I would consider trying include:
1. waiting for the next Chrome update in 4-6 weeks (lazy option) to see if it fixes itself
2. figuring out how to download a beta version of Chrome in the interim to see if that fixes it (impatient, slightly riskier option)
3. doing a clean re-install or rollback to previous version of Chrome after figuring out how to save all my data/cookies/passwords/etc. (probably the most work)
I do not know if any of these things would work, since I don't know what's broken. I don't use Chrome myself, so I'm not experienced with its foibles. But if it were me and I were messing around on my own PC, that's what I'd be thinking.
You could also try to find some kind of specific tech support forum for Google/Chrome and see if they might be able to walk you through a fix. Again - something I've never tried.
ETA: I had another idea for a workaround... there are plugins for Chrome that let you control the volume with keyboard shortcuts (I googled and found
this, just for example). Maybe that would work for you if this is just a total stumper?