In the "About Nitro Pro" window, you will see:
Upgrading your hard drive, motherboard, or even a major Windows update can break the license fingerprint. A license check will tell you if reactivation is needed. Nitro Pro 13 License Check
Activating Nitro Pro 13 is straightforward. If you have just installed the software, follow these steps to complete the license check: Launch the application. Go to Help Tab: Click on the Help tab in the top menu. About Nitro Pro: Click on About Nitro Pro . Activate: Select the Activate button. In the "About Nitro Pro" window, you will
Online activation is the fastest method and requires an active internet connection. Open . Click the Help tab. Click Activate . Enter your 18-digit serial number. Click Activate to complete the process. Manual (Offline) Activation If you have just installed the software, follow
If your computer does not have internet access, or if a firewall blocks the online activation process, you must activate manually using a web certificate.