When trying to put my Product iD, it says that it's already in use when I desactivated it on previous computer, WHAT TO DO PLS!

Hi, I have a student license at school and i’m trying to put storyboard pro 0.7 on my home computer for my homeworks. I first return the selected license to the toon boom license server with license wizard, on the school computer. But when i try to activate ID the license on my home computer, it tells the following: Invallid Activation ID-Key Already In Use. What can I do to make it work on my home computer (which is a mac) via “register a product”.