It could be that your system missing some codec, you may google "WMP has no sound" to find solutions.
Mona
It works using AAC in BD-Ripper, so I'll just assume AC3 is newer and WMP can't handle it. It's been a long time since I had to add codecs to get something to work (back when .divx was a thing & earlier versions of WMP wouldn't play anything but .wmv or other .wm* files).
As far as old ripped files not showing up as proper thumbnails in a folder (but not all of them) and not playing bothers me more. And again, those all run OK in VLC or MP4 Player, so it comes back to Windows.
Thanks for the reply.