Check with your department; your organization may already have a site license you can use.

12.1 may crash frequently on high-resolution displays or modern hardware. Legitimate Alternatives for Researchers

Unauthorized versions may produce inaccurate calculations or corrupt your research files.

SigmaPlot 12.1 was released years ago. Modern operating systems, like Windows 10 and 11, often have compatibility issues with older software versions.

Crack files are frequent carriers of Trojans and ransomware.