Why isn't my cart page working in the default language version?

Hello,

I’m having problem with my language version of the shop. When I add a product and little popup with clickable “cart” shows up there is an error with my language version.

A normal version of clickable URL should be a simple /cart (that’s what shows up in zh-tw version).
Our default language is Traditional-Chinese, but not so sure the url showing for the default language is www.accmask.com/zh-tw. Is there any chance we can remove the zh-tw?

www.accmask.com

Can somebody locate what the problem might be and what we need to change?

Thanks!