: You can enter your email on the Nitro License Portal to retrieve details about your license.

to check your license status or reset your activations manually. Legacy Support

To activate Nitro Pro 11, you need an 18-digit serial number

Nitro Pro 11 , serial numbers are unique 18-digit codes tied to individual purchases and cannot be shared publicly . Additionally, Nitro has officially shut down the activation servers for version 11 and older. How to Find Your Serial Number

If you are trying to move Nitro Pro 11 to a new computer, you must first deactivate it on the old machine to free up the activation slot: About Nitro Pro Activation Deactivate