The Solution Key:

• is a set of four numbers assigned when the licenses are purchased for runtime deployment.
• also identifies the organization that purchased the runtime licenses.
• is set via the SetSolutionKey method of the component’s Licensing class.  For example: 

ScanFix sx = new ScanFix();
sx.License.SetSolutionName("ACMEImaging");
sx.License.SetSolutionKey(0x1C3A023F, 0xA018F260, 0x37AF0E51, 0x557F2389);

The Solution Key must be set in order to use runtime licensing.