Any idea what's going on with this? 

Here is the game in question: https://loressa.itch.io/delve

When played in the browser, my audio works fine, but when installed via the Desktop App no sound plays. Audio is handled via Twine (Sugarcube) through the cacheaudio, createplaylist and audio play commands. Audio files are stored within the game's main folder (there are no subfolders) and are simply retrieved for these commands by their name ("dice.mp3", "lobby.mp3", etc). My only guess is maybe the itch app needs a specific file structure or path for the audio files?

I can report the same issue on the Itch.io Windows Desktop app with my Twine game for audio and videos. I opened a ticket about it on GIthub on February 4 but it never got answered:

https://github.com/itchio/itch.io/issues/1413
I ended up adding a warning inside the game detecting if the user is playing from the Itch.io Windows Desktop app and telling them to use a regular browser. This is a less than ideal solution.

For info, this is what I use to detect the Itch app internal browser:

// Itch.io internal browser
setup.isItchBrowser = function() {
    return navigator.userAgent.includes(" itch/"); 
}