I'm not able to activate my purchase code.

If you see this screen "This feature is available in the full version", it means that you still have the Lite version of the plugin installed:

The Lite version needs to be deactivated/deleted, and the full version installed to be able to activate the license and use all features of the plugin.You can download the full version by logging into our store with the credentials you received when you purchased the plugin via e-mail.

If you already configured Amelia, don’t worry about your data. It is saved in the database, and it will be there after you install the full version.