I have a multi-site with the domain mapping plugin. When I try to map the subdomain to http://computer-it.support, I get the error message that the domain is not active. The primary site is imagineerdesign.com. Both of these domains are pointing to the correct IP: 18.104.22.168
I checked computer-it.support with a DNS tool and it has fully propagated - it is not a new domain.
Further, this was working the first time. It mapped successfully. However, when I went to the site using the domain, it was blank. So I deleted the mapping. It turned out that the site was blank for a another reason. It was looking for a non-existant theme. Once I corrected that the subdomain was fine, but when I tried to map computer-it.support to it, I got the error message.
I uninstalled/reinstalled. Is something stuck in the DB table? When I re-installed it had the same settings which seems to indicate it did not purge the DB on uninstall of the plugin.
I'm running out of ideas. Do you have any?