In the future, please leave a comment on the DLC's Itch page, as this comment section is for the base game.
To solve your problem, make sure to use the latest version of both the base game and the DLC, as it looks like you're using version 5.0 when version 5.5 has already been released. You'll need to delete all previous versions of the game, download and reinstall everything, then restart your PC.
If your problem persists, feel free to leave a comment on the DLC's Itch page and I can try to help further.