Thanks for your inquiry. Every Aspose license carries one-year subscription for free upgrades to new versions released during this time. To check an expiration date of your license open the license file using notepad. You will see the following tags:
It means that you can free upgrade to version of Aspose.Words published before 02/18/2011.
But even if the license is expired you should not get File not found exception. There must be something on your end. Please make sure the license file exists.