Oh, that’s unfortunate…
Then it is most probably a software limitation of Wix and there’s nothing much we can do about that unfortunately.
I’m not totally sure if this is the cause - but this might be why your audio isn’t playing:
For a workaround, I would suggest maybe having a button on your site page that takes the user directly to your presentation’s public URL, and then have a button on the PPT itself, maybe in the last slide, on the corner of all slides - something like BACK TO ALL COURSES which wil bring the users back to your site from there.