I have just purchased a valid license for DraftSight Professional and the license works with my current version V1R5.2.  I want to upgrade to 2015.  I deactivated the license, loaded 2015, and tried to reactivate the same license and it would not do it.  I went back to V1R5.2 and I can reactivate it no problem.  How do I upgrade to 2015?