There can be many issues that makes it unavailable to open this application. My recommendation is to reinstall this software. First of all, uninstall the version that you have on your computer (Control Panel > Uninstall a program), then go to its developer official website and try to download JMatPro directly from there. Then open the setup files and start the installation process. Moreover, on its demo version this application comes with some limitations you need to know about: you are not allowed to make new calculation, you are allowed only to access the pre-calculated data. For the full-featured JMatPro you need to buy it.