MPU9250 :unexpected WHOAMI 0XFF

Hello, Actually i’m going under the exactly same problem.
I’m using raspberry Pi2 + Navio2,

uname -a
Linux navio 4.4.6-4d0ae01-emlid-v7+ #3 SMP PREEMPT Wed Apr 6 13:25:26 MSK 2016 armv7l GNU/Linux

and i have same output above with ‘sudo i2cdetect -y 1’

i checked ‘ps -ef’ and ArduCopter-quad was not working,
and i thought navio shield does not get enough power.
So, i tried power with RC Battery to navio shield and it does change nothing.
It was working well before, and i don’t know why now it’s not working properly.

Is this issue not solved yet?

Thanks,