What do I do if I lost my Serial Number / License Key?
Please submit your request at questionacharge.com with the invoice link or Order ID number.
If you need to re-activate Capture One or activate it on another computer, you can find your license key in your Capture One account as well. Simply log in to your account on captureone.com, navigate to the Manage licenses section, choose the product you need and click on it. Then you will see your license key, the number of activations left, and the activation history.
For more details, check the article - How to find Capture One License Key.