Are you certain that you tried it with the HTML5 client? Can you specify which version, browser and operating system and which languages you tested?
I could not get it to work so far in both Vivaldi and Safari using private sessions (on MacOS 10.12.6)
Currently this makes me not want to use the HTML5 client even though it is vastly better performing than the flash version, because the german localisation uses very different terms from the english one and the latter is simply more consistent and more useful for research and documentation.