I entered my license key under System Info -> License Key.
Unfortunately, this is unlikely to work, as you have a license
activation token which is used by the activation server to generate a
license key for your unique system. It is not quite clear why it has not worked for you.
Licensing matters and issues are better handled privately, as license keys and such are better not shared publicly. Could you get in touch via the contact form
https://featool.com/about/#contact, select "
Licensing Issue" in the drop down box, and submit your "
System Information" (from the "Help" menu) for further troubleshooting (this information is the minimum required to be able to identify your registration attempts in the server logs).
Sorry for the inconvenience.