This tool is designed to write simple Ren'Py games in Twine (already written in Ren'Py language but using the passage jumps of Twine). It will not blanket transform any Twine game into a ready made Ren'Py VN. If you need this for a project I can take a look at the Twine html for testing, feel free to reach out to me at jbtuason/gmail. I have not tested it with any projects using JS.
I tend to think it was the JS code I had put in it - or at least that in combination with a *high* amount of Passages that the program had to try to transcribe. Looking at the output - the code that I managed to transcribe to .rpy file was fine, so I really think It was the amount of passages or the JS code. I had an array in the StoryInit Passage which could have made the program choke or something.
Somehow I don't really think it's the amount of passages... looking at the code context the "Nonetype" error suggests to me that it's checking for passage content for a particular passage when it doesn't exist (I hadn't thought to check if it exists first... but I can add a validation for that in subsequent updates).