After an SSL installation on your web hosting account, you may not be able to open your site. This issue is caused by the SSL installation which requires a DNS change of your domain's A record. Right after the SSL installation, you are still resolving your domain using the old DNS settings.
You should allow a few hours for the DNS change to propagate and take effect. After that you, will be able to access your site without any problems. It is also a good idea, while you are waiting, to clear your browser's cache and your local DNS cache.