I haven't used Captivate 7. But this solutions works with Captivate 6, so it may be worth trying.
If you are seeing the VT folder in your Captivate installation directory (under Program Files),
- Rename the preferences folder, "Captivate 6.0" as "Captivate 6.0_1234" in C:\Users\<username>\AppData\Local\Adobe.
- Run Adobe Captivate as an administrator and you should see NeoSpeech voices in the list.
If you don't have the VT folder, restart your computer and install the NeoSpeech again. This solves the problem sometimes.