SOLUTION:
1. Perform a search for the file "ProductLicenses.xml" on the same drive where the Spotlight Diagnostic Server is installed.
2. Move the file to a separate drive or on a USB thumb drive as a backup or delete the file.
3. Restart the Diagnostic Server service and open Spotlight.
4. Enter in the commercial license key and site message and then close Spotlight and restart the Diagnostic Server service once again.
5. Launch Spotlight again and the commercial key should be maintained.