Voice will install a certificate for the domain automatically provided it is able to validate it.
However, currently you have an AAAA record (for ipv6) on the domain, as well as the A record. But the AAAA record is not pointing to the e-voice server. Hence the validation is failing.
If you delete this AAAA record, leaving only the A record, then the validation will succeed and a certificate will automatically be created for the domain.
Joe - Voice Admin