This game is now blocked in Germany, because of this change:
https://gtm.steamproxy.vip/groups/steamworks/announcements/detail/4678768276768588864

The developer/publisher needs to fill out a survey to have an age rating on the store page if they want to make it available in Germany:
https://partner.steamgames.com/healthcheck/missingratingforgermany/

More information can be found in here:
https://partner.steamgames.com/doc/gettingstarted/contentsurvey/germany

While this change should only affect games, it can also affect DLC, mods, soundtracks and other type of software on Steam. This happens, because Steam doesn't differentiate between a game or other type of software as they all fall under the app category.

There are also bugs that cause the app to become unavailable in Germany if it's linked to another app. For an example, if an app (e.g. game) has an age rating for Germany, but its package is linked to another app (e.g. DLC) that hasn't been rated yet, it causes the other app (game) to become unavailable as well. Even unreleased games suffer from similar bugs if they have a demo available on the store page, so the demo would also need an age rating as it's treated as a different app.