1. Read the following announcement - "Official PTC Mathcad 15 and Prime 1–6 End-of-Sale Announcement": https://community.ptc.com/t5/Mathcad-Tips/Official-PTC-Mathcad-15-and-Prime-1-6-End-of-Sale-Announce...
2. "Mathcad Installation & Licensing Support Center": https://support.ptc.com/support/mathcad_supportCenter.htm