Sonos doesn't "see" WAV files

I have no idea. As I said, metadata for WAV files is non-standard, so therefore I can't say what the differences between those that can be seen and those that can't. Assumedly, the tags are either not getting read by Sonos because they are in other non-standard fields, or they are a resolution and/or bit-depth Sonos does not support (i.e. 96KHz/24-bit files). Without seeing the actual files, we cannot tell you anything about them.

And by the way, there are many music manager applications that will batch convert those files and fill in the tags automatically for you.

You can check if it's a metadata issue by going into your Sonos controller and browsing Music Library > Folders and drill down until you get to the folder where those tracks should be located. If they're listed there, but not in Artist/Album view the metadata on those tracks isn't getting encoded correctly for Sonos. This FAQ goes into an explanation of why WAV tracks may be missing. If the tracks are missing, it could be an issue with the format of the tracks. We'll support WAV tracks up to 1411kbps, so it's good to check the resolution too.