For my current project I downloaded and installed C5.5.0, got it installed and was able to see the plain yogurt theme all was great. Then the trouble started. The theme I wanted to used is only compatible with C5.5.1+. SO, being a newbie, I then deleted all the tables from the MySQL database and installed C5.5.2. Should be good, right? Wrong. I think what is happening is the C5 marketplace thinks I have linked the theme (and an add-on) to the first site. In fact, I have. But that site is now gone. How do I tell the marketplace that I need access for my "new" site to the theme and add-on, again?
BTW, I just discovered the very simple way to update C5 to the latest versions. Again, complete neophyte here.
You'll need to release the themes and add-ons from the previous project and assign them to the new one..
Sign into concrete5.org, go to 'My Account'>> Projects>> select old project>> scroll down and find the addons/themes you want to release>> go to the new project>> assign those licences to the new project.