If you have a shared hosting, a cloud or virtual or dedicated server or service hosting multiple domains, it is normal to face the message.
This site works only in browsers with SNI support.
It’s not an error, it’s a warning message.
It is a thing related to IPv4 and initial days with TLS. We are trying to explain the implication of the error message and in very short, for ordinary websites like a personal website such error in general has no negative impact.
Number of IPv4 is limited and IPv6 unfortunately not so much popular yet.