I have been using the trial version for few days. I've just decided to purchase it today, but when I use the key, it always says "Our activation server is unable to register your copy of Camtasia. You may still use Camtasia throughout your trial period." I want to know how to fix this.
I would open a ticket like Joe suggested. Be sure to include your license key.
If you did not purchase your software key from TechSmith or one of our partners, it's possible that you purchased a counterfeit key and that's the issue. Our support team will be able to let you know for certain.