Hi there,
Thank you for reaching out to us!
Reading through your code, my understanding is that you are trying to implement this using ROPG ( Resource Owner Password Grant ), which at this moment does not support Organization parameters or authentication flows through Auth0’s Organization.
Although we do not have an ETA for this feature, others have voted on it’s implementation and have also shared a potential workaround in the following Product Feedback, but please do keep in mind that the workaround was not provided by an internal Engineer. I do encourage you to also vote on this feature, which will help expedite it’s development.
If a different flow type can be used, we would be happy to take a look and further assist where possible!
Have a great one!
Gerald