Am I right in thinking that you are using the Text to Speech PRO action Generate Text to Speech?
Could you show us the data you get when you test that step in your Zap? A screenshot of the different fields that you get when you test the action would be super helpful. 😊
Don’t forget to remove or obscure any personal or private information in any screenshot you share in the community (eg full name, email address, etc).
We have recently released the Eden AI integration on Zapier that allows you to access to the best providers for each AI technology such as text-to-speech. I believe that this integration could be extremely helpful for your project.