Because the available 2 ddns websites are only in chinese they are imposible to use for a non-chinese speaker.
The solution is to upgrade your software to version V200R003. After the upgrade you will have www.dyndns.org (English website) available.
The cause of this is the out-of-date software version used on the AR router.
Whenever you encouter this kind of issue please refer to the documentation for the latest version of system software. Chances are the issue has been solved in the latest version.