Unable to install Let's Encrypt:
SERVFAIL looking up CAA for example.com
Domain's name servers resolve to a third-party server
Third-party name servers are misconfigured. Name servers CAA record does not exist in Plesk as Plesk so far does not support it. Normally when there is a record like CAA missing on a domain, name server would return "no record" instead of SERVFAIL.
Contact third-party name servers owners to check why they return SERVFAIL error.