Problem: I would like to register my Toolset plugins using new account information, but I see the following message instead of the usual registration panel:
Remember to remove Toolset from this website.
This site is using Toolset plugin, which is not paid for. After receiving a refund, you should remove this plugin from your sites. Using unregistered plugins means that you are not receiving stability and security updates and will ultimately lead to problems running the site. Bought again?
> Check my order status.
> Extend Subscription.

Solution:
Add your new site key to your wp-config.php file using the following syntax, to programmatically register the plugins:

define('OTGS_INSTALLER_SITE_KEY_TOOLSET', 'ABCDEFGHIJKL');

Replace ABCDEFGHIJKL with the actual registration key generated for this site in @https://toolset.com/account/sites

Relevant Documentation:
https://toolset.com/faq/how-to-install-and-register-toolset/#automatic-toolset-registration-using-php