Many of those issues will require intervention from Domino Support. One of the more common and easy to fix reasons for getting this error is if you have used 'www' in the url for your Domino Deployment. For example if your domino Deployment is located at https://mydomino.mycompany.com, but you accidentally enter the URL as https://www.mydomino.mycompanycom.
This is of course a relatively easy issue to correct, just remove the www from your URL. Note that once you have typed the www address in once, your browser cache will often take you back to that same address even if you enter it correctly the next time. So you may need to clear your browser cache. Also note that the 'www' may not be visible until you click in to the URI bar as in the screenshots above.