Find a file in Documentlibary not working. SearchCenter is working

Hello

We have a problem with the searchbox "find a file" in all lists. There are no documents found, if we enter a term

If we search with the "Search Center/Enterprise Search" we got correct hits. 

In the SearchAdmin "Crawl log" I find the documents in "Successes" lists.

I don't understand, that the documents won't show up.

Thanks for a tipp or two

Best regards
Moritz