The first thing you should do is try to confirm what the issue may be. Check to see what is displayed on screen when you attempt to access your portal. Is it displaying an error message?
If the error message states the site is in maintenance mode, you will need to access the Admin Portal and turn off 'Maintenance Mode' in the Site Settings.
If the message is a HTTP error (unable to find site / site timed out), attempt to load another website, such as www.google.com, to confirm if your internet connection is causing issues.
Clearing your browser history and browser cache can also help in resolving issues. If you are unsure of how to do this, the help page on your browser should be able to assist.
If, after attempting the above steps, the issue is not resolved, contact support at support@mediasphere.com.au.