Language switch issue: changing language always redirects to the first page

[AnSennLi]

Hello, everyone.  My store has launched for months and this issue happened recently and I can not figurer it out why. My store is supposed to support English, the default language, and also Simplified Chinese, Spanish, and Russian. But once when I attempt to change the language by clicking the language switch, the site always fails to load the selected language and redirects itself back to the homepage. No matter where I switch the language from English to the others, it always goes back to the homepage.

This is my store's link: fallon-fj.com,

I want to know why or if there is anything wrong with my theme.

Thank you very much.