The HyperText Transfer Protocol (HTTP) 505 #HTTP Version Not Supported response status code #error indicates that the HTTP version used in the request is not supported by the #server.
So if you see this error in your Web browser, the only option is to upgrade the Web server software. If version 1. x requests fail, it may well be because the Web server is supporting the 1. x protocol versions badly, rather than not supporting them at all.
More info >>
https://ibmimedia.com/blog/77/solve-error-505-http-version-not-supported
