I have uninstalled Music Maker 2015, and installed it on another drive due to lack of space. When I reinstalled it, it openend the window to put in the Activation code and email. I did, but it started loading infinitely. I let it continue for 30 minutes, then gave up.
Most obvious question, perhaps: does your computer have internet access and/or could your AV or firewall be blocking MM from accessing the Magix server?