Yeah, it's weird. I'll get notifications for everything else (including Patreon having coupons?) just not messages.
The way renpy handles gallery unlocks is through persistent data. If it flags that you've 'experienced' the content, it'll unlock. Except when arbitrarily it decides it won't unlock because of reasons. These reasons are completely alien and not explained at all. In testing, it also decided it wanted to un-complete my gallery for seemingly no reason so I can only assume this is a renpy problem and not something I can solve outside coding in a master unlock password or some hard check at some point to force unlock everything in the gallery. But given the tendency for renpy to also just ignore code, that might not work either.
Yeah, ive noticed this same issue in previous builds where the gallrry would display "Gallery Completed", yet the last image added would still be locked. Its fixed now, but im thinking it might be the same predicament happening for the music gallery as well, since this is the first track being added in a long time.