Nice to see a fully-translated German CodeRunner site, Martin. Looks great :-)
But therein lies the problem. It turns out there was another condition for the button to be displayed, namely that the result table has two columns headed 'Expected' and 'Got'. Which of course doesn't happen on a German language site! This isn't a new bug - it has always been like that, but you've only just hit it as a result of translating all the language strings.
I've fixed it (I hope) in my development system by using the correct language strings. The fix will appear when I next merge and push the master. In the mean time, if you want to live on the bleeding edge you could pull the latest development branch from github.
Thanks for reporting