Hiya,
Sounds to me (Although I'm not the one of the devs, or an expert for that matter!) like you're restoring the licence, but not using the MJR file to activate MC
When you enter the code, a mjr file should be generated & downloaded to your computer. If you double-click this new file, MC should open & load its licence information & then stay registered from then onwards.
Cheers
-Leezer-