This is the same problem I experienced when this was given away before.
When I signed up for this & tried to create an ebook this is the message I get:
“There has been a problem connecting to the AI. Your OpenAI API key is either missing or invalid – Please set it correctly in your Settings dashboard.”
There is nothing in the settings to set this up, & there is no explanation of how to fix this problem.
Also this is a web only app that you have to use online, which is a bummer.