Well, i just sent mine back to DJI for repair or replacement and they have recieved it today. Hopefuly i should have an answer by the end of the week as to what the problem is. I'll keep you posted ?
Have you sorted it out yet? I have the same problem with my mavic mini... no GPS whatsoever (even on a football field on a sunny day). Tried everything DJI support told me, still nothing.