Could not send message: Unexpected token 'H', "Hello ther"... is not valid JSON

Hi there, first-time user, never coded before and now learning on the fly with AI by building a web app using Replit.

I've added my first chatbot to the web app and it's appearing as expected but when I start talking with the bot it gives me this: "Could not send message: Unexpected token 'H', "Hello ther"... is not valid JSON"

I've spent a few hours implementing different ideas proposed by AI but alas, the same issue. How do I resolve it?

For the context, the buildship flow is attached.

Any help is much appreciated.