I have the same issue.
It seems that hestiacp does not do it out of the box anymore, the solution that was posted to me was that you have to set the dns records for it in hestiacp but the default system admin account but I have not been able to do this without disabling the security policy that stops other users adding dns records, sub-domains etc for that domain.
Setting the dns nameservers in your registrar that points to your hestia install prevents you from adding dns records in the registrar as they are not handling the DNS anymore but Hestiacp is.