Did you post this on the PT3 forums too? I replied to a post about an issue like this over there.
I'm guessing you didn't already have a full license for PT3 so you must have been on the trial?
If so, you could revert to using the trial by closing PT3 down and deleting your license file (C:\Program Files\PokerTracker 3\Data\Config\PokerTracker.lic). When your trial ends you can re-enter your license code to start using it again as a registered user at Party only.
Alternatively you can upgrade to the full version from our
Purchase Page - you will pay a discounted price to upgrade from the Party-only version.