Our game, Muse Dash, used to have a category but it appears to have gone missing randomly. Not only is it missing, I can no longer re-add it - there’s “Muse Dash”, but no “Muse Dash” from the add game dropdown, even though it appears in the giant bomb: [Muse Dash (Game) - Giant Bomb).
Checkon on IGDB I find https://www.igdb.com/games/muse-dash--1 which suggests a duplicate was deleted and Twitch hasn’t reaborbed the non duplicate yet.