This happens because the License Upgrader expects a site code of six letters followed by two digits. This error is shown when the upgrader finds a registry file that doesn't match this pattern. You might see this error in two cases:
1. You have other registry files in either the same folder as PharosLicenseUpgrader.exe, or in your Pharos\Bin directory. In this case, it is recommended you move the upgrader executable and the correct license file to a new folder.
2. You have a five letter site code. In this case, you can work around the issue by adding an extra letter to the registry filename.
For example: SCODE99.REG could be renamed to STCODE99.REG or SCODEX99.REG.
The filename must be exactly six letters, and two numbers.
Adding an additional letter to the registry file name will not affect your actual site code, and will not cause any trouble with license renewals in the future.