Hi @rueben.tiow,
Thank you, it works now after added required permission per your instruction.
I would suggest to put a similar screenshot like yours to this step Register Machine-to-Machine Applications to make the documentation more clearer 
as the collapse icon is quite unnoticeable to the user (or at least to me).
I have skimmed through the docs multiple times but can’t see any place to guide user to click to that collapse icon for adding permissions (or I might be missed it)
A quick one, can I use the Auth0 Management API (Test Application) for Production purpose? Not sure about the postfix Test Application means anything?
Thank you again for your kind support.