You need to modify parameters within the Mavic Pro itself to enable flights in NFZ.
These params are available in .700 and below, I’m unsure if they’re available in newer firmware versions?
At the time of posting the thread below, it wasn’t even possible to roll back newer firmwares, now it is 
You could try (without risking anything) by using an old version of DJI Assistant and putting it in debug mode, check this one out Dave:
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