12306.cn accepts only UnionPay cards, Chinese bank cards, and Alipay/WeChat Pay. Foreign Visa/Mastercard/AmEx are NOT supported on the official site.
Use Trip.com (English, accepts all major foreign cards, 24/7 English support) instead — same prices as 12306 plus a small service fee. Alternatively, book at any train station kiosk or counter with cash/passport.

