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.
Server With SNI, can enable multiple SSL certificates on a single IP.
Some websites have one IP = Website, you can imagen that will use limeted IP address fast, so we use SNI. SNI stands for server name indication, this means that one IP on a server can open multiple domains, then obviously the IP will not open one website.
So if you see this warning message it means that your website is on a server that is using SNI.