Thanks for your support.
I think I understand the issue and what you are trying to do. If you like, I can take a look into your website and check out what is going on, just email me temporary admin login details.
Else if you want to try yourself, firstly just to be safe, make a backup of your code blocks via copying your code to a text editor, or if you prefer, just backup your database.
You would need to deactivate and delete CJT Core from Plugins. This is not used or needed by CJT PLUS that you just purchased. In fact, you should be able to deactivate all your licenses and reset the fields before deactivating and deleting CJT Core. You also should deactivate and delete the previous version of CJT PLUS. Since your code is contained within the database, this should carry across just fine to the new versions.
Once you have installed and activated CJT Free from WordPress (link above), you can then upload, install and activate the premium CJT PLUS version you just purchased. Click the Setup link in CJT PLUS (in Plugins) and you should be able to enter your license key you received.
Let me know how you go.