Drawboard PDF moved to a subscription-based model in 2016 to support ongoing development. This means most users will not find a standalone "activation key" for purchase outside of official channels.

An authentic is typically only issued to business or enterprise users through volume licensing arrangements, where keys are device-based for sideloaded application packages . For individual users, the "Pro" features are unlocked through a subscription tied directly to your Microsoft Store or Drawboard Cloud account , rather than a manual alphanumeric key. Understanding Drawboard PDF Licensing

This can happen if you reinstall Windows, use a different Microsoft account, or if a trial expired. Log in again with your original account and use “Restore Purchase” or re-enter your key.