This error normally occurs due to the following reasons:
1) The website’s files are not in the https directory on the web server. This can be verified by trying to get to the file using a regular, unsecured “http” call, and checking if the web pages are loading correctly. In order to correct this problem, please add the files to the https directory defined in the SSL configuration of the web server.
2) Port 443 is blocked by the server's firewall or the end user's firewall. In order to correct this, you must open up port 443 (for both inbound and outbound traffic) on the server's or user's firewall.
3) The https server is down. This can be verified by checking your respective web server’s task manager. Please ensure that the server running https service is up.
4) Incomplete SSL certificate. In this particular case, it is possible that your SSL certificate does not have a corresponding private key file. Please refer to the appropriate installation documents on our support site for your web server, and verify that you've installed the SSL certificate correctly by having the corresponding private key file.
5) The web browser is not set to SSL 3.0. Set 'Use SSL 3.0' option in your browser.
