Lumen RT 2015 re-install software missing activation key

Our office bought a Lumen RT 4 license from E-ON software in 2013 and upgraded the next year to Lumen RT 2015. I have the original Lumen RT 4 activation file (key). When we upgraded to 2015 we activated the software online, but can't seem to find the 2015 activation key file. We had to uninstall the software on the machine and would like to re-install it. When I ran the 2015 exe file it is prompting us to  to activate Lumen RT 2015 again.  I cant find the original file and when I try to go online to request it, the web link does not work. How do I request the activation key file for LumenRT 2015?

Our Installation Code is INST-SDSJH-CDJMC-ZXQDD-QDCHB-LPFBL-LHJCF-CFN-LRT5STD

Thank you in advance