I do not understand what to do, you send an email:
"Attached, please find your requested license file for Mathcad, which enables you to run the Mathcad application.
If necessary, you can now complete the installation and licensing process with this file.
Save this file to any location (e.g. c:/temp or any other location of your choosing). Please be sure to remember where you saved the
file since you will need to reference it later. The file must be on the same hard drive as your installation of Mathcad. When you attempt
to launch Mathcad, you will be asked to specify the path to this file.
Please do not open the attached file through your email application as that can corrupt the file. Be sure to save it to disk before opening
or unzipping it.
For all future licensing requests please use the Mathcad Installation & Licensing Support Center:
The PTC Licensing Team"
Did you verifed if the getting file is Unzipped? Please ensure that the file you are browsing during the license activation is a *.txt file.
Which version of Mathacd is installed on your machine? if yes, please follow the bellow steps:
5. Select “Use a license file” and click on the circled button shown below
6. In the Open dialogue box, browse and select the saved license file and then click on open (Note: change the file type to All files, if required)
7. Click on Next > Finish