Update: It seems pretty clear now that it's an account corruption issue.

I uninstalled the game and reinstalled it. I tried logging in with my account, and I was then stuck in the same startup screen.

I uninstalled the game and reinstalled it again. I created a new account, and now I am able to play again, but completely from scratch, and I missed out on the Starter Pack sale.

Is it possible to restore the previous account and get the Starter Pack at the sale price? I'm a firm believer in spending money on things I like to reward the people who put the work into it, be it music or games or what have you. Especially because I have friends in the games industry and the music industry.