wav files suddenly won't open

You don't say what you have already tried. For example, have you already 'right clicked' one of the .WAV files and selected Windows Media Player when the drop down menu offers choices to 'Open with'? Set the Windows Media Player as the default application to open your WAV files. (These instructions may be incorrect because I'm writing this from memory. I don't have my W10 laptop with me at the moment.)

If you've already tried this, post again saying what you have tried and give more information about the update you carried out and which operating sytem you are using.

Seems to be a common problem. Have you tried googling? There seem to be some possible answers including this:
www.lifewire.com/wav-wave-files-2622395

I don't know either but will post to bump this.

Sorry, I don’t know, just bumping your post in the hope that someone tech savvy sees it. (You could try googling the question).