Solved! Go to Solution.
Mathcad 15's trial has been disabled because Mathcad 15 has been end-of-saled: https://community.ptc.com/t5/PTC-Mathcad-Tips/Official-PTC-Mathcad-15-and-Prime-1-6-End-of-Sale-Announcement/m-p/715557#M132
Mathcad 15's trial has been disabled because Mathcad 15 has been end-of-saled: https://community.ptc.com/t5/PTC-Mathcad-Tips/Official-PTC-Mathcad-15-and-Prime-1-6-End-of-Sale-Announcement/m-p/715557#M132