I have the same problem, after the WP update, the pages in other languages don’t appear (only with the main language works). @chouby you could check the web: https://www.waveex.at/
@dani3c, @masakmand @chouby This trick worked for me: In the Permalink-Settings /wp-admin/options-permalink.php i changed to the first option to call the page with id. And than back to the option with url-alias. Now they are working fine.