We have had this discussion a lot recently. What route are you trying to reserve ?

One cannot treat the mainland Chinese airlines like how western airlines work, e.g easily reserve and manage a résa on their websites, because that is not how the very large local population works. The chinese airlines do most of the business on their applications and Mini-applis on Wechat. So adjust expectations accordingly.

I have been recently able to make résa on CZ's main website, but it's not always the best price and managing it is haphazard luck sometimes, I end up calling or emailing their call centre in China (which is efficient btw).

With mainland Chinese airlines :

• direct résa isn't seamless.
• Managing résa on their website is not always successful
• Booking early doesn't always yield the best prices especially for domestic mainland flights
• It can get difficult without a Chinese mobile phone number.
• Using their mini-programmes or applis are better and more accurate, but these are in 中文