Is it saying "failed to open page" or are you getting a notice the site isn't secure?
I have an old Mac and it won't update my browsers any more, kept getting the not secure, certificate invalid notice.
If that's what you're getting, when you see the notice, you can type thisisunsafe (not in the address bar, just click on a blank area and type it). It will override it and let you in. You do this at your own risk. I'm just saying it worked for me and so far I've had no issues. I think it's just that my computer is too old and outdated.
If that's not the issue, not to insult you, but are you able to go to other sites? Have you checked your internet connection?
What browser are you using? You may need to clear cache and cookies. You can google how to do that for your browser. Sometimes old information your computer stores for websites conflicts with new information, so you have to clear the old.
