Your domain is not yet pointing to our nameservers ns1.infinityfree.com and ns2.infinityfree.com. Please change your nameservers at your domain name provider and wait a few hours for the change to take effect. You can also create an account with a subdomain first.
Other Information
The domain is currently held by simply . com. The error message seems to suggest that control of the domain name must be transferred to infinityfree before I can create an account. The simply . com support, on the other hand, says that they cannot change the nameserver before infinityfree has accepted the domain. So I seem to be stuck with no way to proceed.