Serps don’t index 4XX pages because they don’t do the job. Therefore, they’ll ignore any canonical tags pointing to these kinds of pages and often finish up indexing the incorrect (non-canonical) version of your website page. For anyone who is using a CMS like WordPress, Joomla, or another System, there are https://xyzbookmarks.com/story18655657/everything-about-hreflang-to-non-canonical