Be careful, the old version of the registrar have bug
Two days ago, I registered a domain name through mew in the old version of the registrar but I forgot the name ens app and enssimple can not display this domain name Why? Is there any program that can display all the complete ens names?

It’s not possible to register a name using the old registrar any longer. How exactly did you register it?

sorry for my bad english,I have already registered successfully, but I forgot my domain name. I can’t find it.

Forgetting your domain name is not a bug on the registrar, it’s a bug on you.
You register a hash, so the registrar is not aware of the domain name behind the hash at any point. Also, you should not be using the old registrar anymore.

Your domain is 4000000.eth

No, 4000000.eth is registered for 2017
I registered another one a few days ago.