Problem Solved - Sharing for Others
I was having trouble launching this game directly from the executable file. Every time I tried to run the .exe, I got an error message saying the game must be launched through Steam instead.
After some testing, I found a working solution. You need to claim the companion pass from the Steam store first. The trick is you don’t actually need to install it completely. Just add it to your library and then you can stop the download right away.
Once you do this, the game will load properly into the main menu without any issues. Hope this helps anyone else running into the same problem!