When installing a free Let's Encrypt certificate the following notification may be displayed:
In the first case, it is enough just to wait until the cache in the system is updated. DNSand retry installing the certificate later. As a rule, updating the cache takes several hours (in rare cases, up to 24 hours). For more details on the cache DNS can be found here.
In the second case, you need to specify in the address records of the domain the current IP addresses of the hosting account... After making changes, it will also take some time to update the cache in the system DNS.
If the domain is served on third-party NS, then changes need to be made not in our panel, but in the panel of the owner of these NS. To direct a domain to our hosting, you can use instruction.