I had a hell of a time trying to calibrate the IMU, stuck at step to - error 71 etc.
The instructions on the app are a little misleading as it looks like the drone should lay flat on the ground -
Sparky has to stand up on its props!
2 props on the ground 2 props pointing up - now rotate as instructed and it should all be well.
This might seem to be common knowledge for some of us but for those with issues, here is the solution.
Hope this helps!

Good tip. The supplied images can be a bit confusing. Reference the DJI logo in the picture for more clarity.

Thanks for reminder. The IMU calibration tutorial video is in preparation and we will release it soon.

i would remove the props..

That would be proper procedure, thanks for pointing that out