Help connecting to Internet Explorer

Hi,
I've have tried to connect to the internet through Internet Explorer and I get an error message all the time stating: "Internet Explorer cannot display the webpage." I have good internet connection with google chrome and mozilla firefox but Internet Explorer isn't working. I need Internet Explorer because this is the only website that works for my school's website. I've tried everything like resetting my internet explorer settings (through internet options), enabling all the tls and ssl from tools> internet options> advanced> and under the security settings to working offline. Nothing seem to work. I don't know if it is just my AVG firewall which has the original Internet Explorer application allowed (but that still doesn't work). So I added a "copy/shortcut" of Internet Explorer to the "allowed" list of my firewall applications but that still didn't work (maybe because it's not the original internet explorer version I need to add. Hence, what should I do? Please help. Your input is greatly appreciated! Hope you understand