The community will undergo maintenance on October 16th at 10:00 PM PDT and will be unavailable for up to one hour.
Kinda wondering who told you that.
These no longer apply to Mathcad 15 for years now. Your Mathcad Prime licences only entitle you to Mathcad Prime 7 through 10+.
See this announcement: https://community.ptc.com/t5/Mathcad-Tips/Official-PTC-Mathcad-15-and-Prime-1-6-End-of-Sale-Announcement/ta-p/818870