I am also struggling with this.
I originally found the flight I wanted on another website for only $900, but it gives me an error and when I called them they said the flight did not exist anymore.
en.ceair.com gives the error the OP says and there is no phone support.
hk.ceair.com finds the flight for $1200 but requires 'travel documents' (which I believe is related to citizenship in hongkong, because the flight I am attempting to take would not require visa documentation, passport only) to check out, and customer support is an international number that I am unable to call.
2013.ceair.com is a chinese website that can be used if translated with google translate, but tickets cost over $2500 for my flight. 2013.ceair.com has a support phone number but they speak poor english and were unable to lower the price.