If you are using SAPI speech engine for the radio/passenger information systems in RW Enhancer 2 (which is the default configuration). You must install some required voices packages in windows.

For RW Enhancer 2 you must install those following packages:

• English (United States)
• English (United Kingdom)
• German (Deutshland)
• French (France)

To install those voices packages in windows go to: Settings > Time & Language > Speech

And click on the 'Add Voices' button (see the green circle on the image below).