not wipe user data

[M.S.khan]

Hi, Friends I have a tablet model No sanei N83 delux but it now lock with google username and password I am wiping this by adb or fastboot
when I am connecting with ADB or Fastboot it's connected but when I am wiping then it's show me this massage ''Error opendir' ing /data ' Permission denied'
so any body give me the best solution to solve it
Thanks in advance