Comentário oficial
You have to do all of the getting cleared on the DJI FlySafe site. It sounds like you did that. Then you have to connect using the DJI app and log in to your DJI account so all of the NFZs you are unlocked for will be loaded on the aircraft. Verify that you are unlocked in the DJI app. Once it is all loaded on the aircraft you should be able to take off using Map Pilot Pro within the NFZ.
If you still can't take off make sure the altitude you are flying does not cross into the maximum defined altitude for that NFZ at any waypoint locations.
It does appear that there are certain types of NFZs that do not allow waypoint flight within them.