You've translated your whole site into German. The pages are live, the translators are paid, and the German version gets almost no search traffic.
There's a good chance search engines have never seen it. If the German pages live at the same URLs as the English ones, and your server picks the language from a cookie or the visitor's IP address, a crawler only ever sees one version. Googlebot mostly crawls from the US and doesn't send an Accept-Language header, so as far as it knows, your site is in English.
Every language version of your site needs its own address. This chapter covers how to choose that address, how to tell search engines which versions belong together, and why translating your pages word for word isn't the same as being found in another market, and how to make sure the pages load quickly once people in that market find them.