Each time you install a free update, you'll be prompted to re-activate your software. This is normal behavior. The good news is that the software remembers your serial number, so you just have to clickActivate to complete the process.
Tip: Sometimes, strict security measures can prevent Articulate software from seeing the serial number stored on your computer. If your serial number is missing from the activation form after updating your software, copy and paste it from your purchase confirmation email. If you need help, let us know.