Hi The standalone provider (= offline) won't work with IL2CPP. You will need either MaryTTS or AWS Polly as solution. With the new update, Klattersynth is also working offline. We're still waiting for a fix from Unity. Please vote on the issue here: https://issuetracker.unity3d.com/is...process-dot-start-fails-to-launch-application Cheers Stefan Edit: RT-Voice works now with Windows standalone and IL2CPP builds!