MindMapper 16 license format has been changed from 4 fields to 2 fields to cut down on the registration process. Name, Email, Serial, and Registration fields have been reduced to Name and Serial number. However, serial number now consists of the old serial number plus the registration number.
So if you have the 4-field license, you would have to fill in the name and serial number and registration number into the Serial # field to activate MindMapper 16. MindMapper 14 and below have 4 fields still.