The site preview was probably not working because you added a master template that did not have the default content include. Without this, the system cannot display anything on the site.

Take a look at the master template. To find out which template is the master template, go to

Tools > Settings and look for the Master Template. Once you locate it open it and if you cannot see an element that says  "Component Include - Templates Content Components" you must add it.

To add it, drag a component include element from the element tray and when the properties box appears, click the check box that says "Include the Templates Content Components" and then press save.