HTTP 505 HTTP Version Not Supported means the server does not support the major HTTP protocol version used in the request. For example, the client sent an HTTP/2 request to a server that only supports HTTP/1.1.
The client is using a newer HTTP version than the server supports.
Try the request with HTTP/1.1.
curl --http1.1 https://example.com/
Upgrade the web server software to support modern HTTP versions.