Why does dnserror work in IE11 when it works in everyone else?

Question

Internet Explorer

There is a corp. a website that stupidly stopped working inside the corp. network in IE, before http-headers was pure Apache now running ngnix. Yes, the site works over ssl.

Any normal browser opens, but IE first writes "RC4 algorithms not found, turn me on all TLS variations" then "page is not available" and it refers to iframe/dnserror.htm, therefore it does not reach the web server at all.

where to look, how to treat?

Patient globally not functioning :(