In most cases, such an error appears if the Purchase Code was registered through another support account. If you do not have access to this your account follow these steps to handle the case:
Log out from the current account on the support website (skip this if you is not logged)
Login with Envato account
Thus, our system verifies the owner of the license and binds the purchase code to the email that is linked to the Envato account. For previous support accounts, the purchase code will be reset.
To reset the license key from the website, go to the Consulting > Product Registration section on the WordPress dashboard. Click Deactivate button, you will receive a notification that you agree to deactivate, press the Ok button and the system reset the license key from the website and deletes the theme automatically.
Yes. According to the ThemeForest license terms, one license key allowed to be used on one project. One Project contains one live website and one staging website. If you wish to use Consulting on an additional project, it requires you to buy another license.
Yes. You can keep the theme on a staging site to build it, then move it to the live site once you have finished. See the following page about the license key transferring: