@brenover Do you have sounds anywhere in Opera? If not, goto settings -> system -> sound -> volume mixer in Windows and choose to reset the volume for all apps. Try the reset while Opera is open and while Opera is closed.
If that doesn't do the trick, while Opera is open and playing a video with audio, check Opera's specific volume in the volume mixer. You can also check it in the old volume mixer by hitting Windows key + r, typing sndvol and pressing enter.
You can also check that the default sound device is correct in settings -> system -> sound in Windows. You can check that the old way too by hitting Windows key + r, typing mmsys.cpl and pressing enter.