Thank you for your response.
The "Organization is not allowed for this client" error happens when the Application’s Organization setting has selected Individuals for personal use:
In this situation, I recommend changing the “What types of end-users will access this application?” value in the Application’s setting page (Auth0 Dashboard > Applications > Applications > Your Application > Organizations tab > Scroll down to the Organization Settings box) to either Both or Team members of organizations.
After this is complete, this error should go away. Could you please let me know how this goes for you?
Thanks,
Rueben