You can purchase a legitimate license through the Grafiti Shop or Systat Software . Locating Your Serial Number:

Cracked software is a primary delivery method for malware. When you download an "activator" or "keygen," you are essentially running code from an unverified source that has been designed to bypass security protocols. Spyware & Identity Theft: These files often contain hidden spyware or keyloggers

If already installed, go to Help > License Status or About SigmaPlot to see active registration details.

To my surprise, a kind user responded with a helpful suggestion. They informed me that SigmaPlot offered a free trial extension for researchers and students. I applied for the extension and provided the required documentation. A few days later, I received an email with a new serial number that was valid for a year.

John had purchased a legitimate copy of SigmaPlot 12.1 a few years ago, but the license had been tied to his old computer, which had since crashed. He had tried to contact Systat, the software's developer, to request a replacement serial number, but their customer support had been unhelpful.