Mac App Store Problem

Hey There,

today i bought a second hand MacBook Pro (mid2012). I startet it an everything went well. i did not sign in at any account. The Mac App Store told me, sierra has to be installed. So i did.

After a while sierra was installed and the Mac restarted. After that, i decided to do a fresh install without any things from the preowner. I signed up in the app store with my apple ID and went to "gekaufte Artikel" (Sorry thats the German Version, in English it must be smth like "Bought stuff")

I wanted to make an bootable USB-Stick, but i could not find the Sierra installation Programm. The Screen was totaly white. Nothing was shown. After i searched the whole Mac i decided to sign off the Mac App Store, and there it was. But "A Problem accured" so i could not download the Program any way.

Now im signed out and the Programm is loading, but why doesnt the App appear while i am logged in at the Mac App Store.

Thanks