Domain mapping plugin unavailable

Here is what I did with it:
1\ weme.im installed with wpmu on a (mt)gridserver;
2\ wildcard domain record added with weme.im;
3\ dimsomme.com is added as an alternative domain on the same server and with 'A' record to the dedicated IP address of weme.im;
4\ we-space.cn is added with 'A' record to the IP address dedicated of weme.im, located on the other host;
5\ domain mapping plugin installed with weme.im;
6\ add 2 multisites named dimsomme.weme.im and space.weme.im as subdomains on weme.im;
7\ try domain mapping dimsomme.com and we-space.cn to the subdomains above;
...

Now comes the error_

<b>Domain name is unavailable to access.</b>
<small>We can’t access your new domain. Mapping a new domains can take as little as 15 minutes to resolve but in some cases can take up to 72 hours, so please wait if you just bought it. If it is an existing domain and has already been fully propagated, check your DNS records are configured correctly.</small>