On Magix Music Maker 2021 Premium, every time I download content, it says installed but never shows up in my library. When I close out the program I have to download it again and it still doesn't show up in my library. I also just updated it too. I am using Windows 10.
You will see from that bugs list that a few have already been at least partially "squashed". Whether/when the rest will be similarly removed only Magix staff and developers know! We are all merely users.