Reflector 2 uses a new-style license key. This key is much shorter than the original key for Reflector.
Old style keys are very long strings of random characters. These keys often exceed 100 characters.
New style keys follow this format:
If you are seeing an error message stating your key is invalid, then you have downloaded Reflector 1, not Reflector 2. Please remove Reflector, then download Reflector 2 from here and give your key another try!