Need help to enable Mathcad 14

I am an existing user of Mathcad 14 and have used Mathcad for over 15 years. I bought a new laptop using Windows 11 and installed the program. When attempting to license the program for which I have the product code on the original envelope I'm unable to do so. The response is: "The trial program you are requesting is no longer available. Please visit...ptc.com to explore our latest versions." This is false I'm not requesting a trial program I already have a non-trial program. I tried to access my existing PTC account and wound up creating a new Basic account in an attempt to get help. I'm an 83-year-old retiree and need help to enable Mathcad 14. Any assistance in solving this problem would be most appreciated.