I am having a strange issue with the website https://www.educationumbrella.com/account.register the website works fine in firefox and in chrome but wont work in IE the page display

" The proxy server isn't responding

•Check your proxy settings. Go to Tools > Internet Options > Connections. If you are on a LAN, click "LAN settings".
•Make sure your firewall settings aren't blocking your web access.
•Ask your system administrator for help. "

I bypass our proxy server and have even tested it through our proxy and it works fine in chrome or firefox but not in IE have gone through IE settings and cant see any obvious

any advice?