• Licenses for many Steinberg programs are stored in the so called Soft-eLicenser, a virtual license container on the hard disk.
• Each Soft-eLicenser has a unique number which is required for the software registration and license activation. 
• The Soft-eLicenser is represented by a hard disk symbol in the eLicenser Control Center - the license managing tool used by all Steinberg programs.
• The eLicenser Control Center can be found under Applications (Mac) resp. Programs (Windows). 

Problem

On trying to activate a license an error message comes up:

'Unfortunately, the serial number of your Soft-eLicenser is not unique'

Solution

Please download and install the latest available eLicenser Control Center version from here.
The current versions (starting with 6.10.2.18194) can regenerate the invalid Soft-eLicenser number automatically and the activation of a license should work after the installation.