The following is copied from the NeoSpeech website and provided here only as a convenience.  Updated instructions may be available from NeoSpeech.  The original link this came from is:

http://www.neospeech.com/faq/the-tts-desktop-application-plays-a-demo-notification-even-with-my-purchased-license-in-place

Symptom:  The TTS engine plays a demo notification even with my purchased license in place. What do I do?

There are few reasons why VoiceText(TM) engine (desktop app), such as VT Editor and SAPI, plays a demo notification.

Please check the following:

   1. Restart the application once the license is put in place.

   2. Make sure the license file name is "verification.txt" without any typos.

   3. Make sure that there are no line breaks in the license string in verification.txt. It should be a single line.

   4. Make sure the license file is in the "verify" directory under the correct installation path.
        - e.g. C:\Program Files\VW\VT\Kate\M16\data-common\verify

   5. Make sure the MAC address of the system's NIC matches the MAC address listed in the license file.
        - To find out the MAC address of the system, run "ipconfig /all" from a command prompt and look for "Physical Address".
        - Make sure the MAC address is tied to an IP address.
        - Only the hexadecimal number needs to match (ignore dashes).

   6. Make sure the TTS version matches with the license version number.
       - To find out the version number of VoiceText(TM) Engine (desktop app):
             1) Open the TTS desktop app
             2) Click on Help → About...
        - To find out the version number of the license (verification.txt), look for "version="3.11.x.x"".