I was wondering why my VODS on twitch had no audio in them, then I see it's a common issue with people who have soundtrack, as a reddit user pointed out: "Seems like it's related to the Twitch Soundtrack plugin which I noticed you use. Its intended to remove music from VODs but a lot of people have been having issues with getting everything routed correctly despite following the exact instructions." https://www.reddit.com/r/Twitch/comments/jw6ovc/no_game_audio_nor_discord_audio_in_vods_but_can/

Same type of thing on OBS Forums: https://obsproject.com/forum/threads/any-idea-why-my-in-game-sound-is-muted-in-vod-but-works-when-live-mic-works-for-both-twitch.131970/