Your activation came from the same hardware you have always used, so the activation doesn't count against you. You can install and uninstall on the same machine as many times as you like, including activating. My guess is you decided to do a fresh 10.3 install rather than an update, so you likely (I assume) re-installed SkyMaxx Pro to this new install, which prompted an activation because license data is stored locally in the specific X-Plane install. No need to worry.