If you are trying to flash Mavic 2 with NLD after you've upgraded with DJI assistant, you won't be able to flash it with NLD. So in other words, if your Mavic 2 has the latest firmware upgraded with DJI Assistant or app, you can't do it.
Yes, I know, on the day I bought the program I did 7/26/19 upgrade. Bad luck. That's why I immediately wrote to the author hoping for a reaction. I didn't get a clear answer whether the program will work or not in the next upgrade. It's not about money either! I only expect an answer - is there a chance for a working patch ?!