Yeah the same thing happened to me, you can play the game normally first before seeing if you even want the DLC, DLC doesnt add anything of value so you dont need to worry about missing out.

DLC should probably only be done after beating the game anyway, it was kind of annoying trying to do it at the same time as the main game.

I had the same thing happen to me. It ended up i had to go to the steam store page and click the "add to library" button on the DLC, and it fixed it !