It should be in your account on the main shop (not here on the forum).
In some cases like Ace it's the order number, but I don't know if that's the same for IGM.
You also need to make sure that your IGM is fully updated, because one of the updates changed the DRM a few years in the past.
If nothing helps, you need to send a sales support ticket through the support system top right - we on the forums have no access to Degica's database for checking. If the ticket asks for a S/N, just fill that with zeroes and explain in the ticket what it is about.
