> adb shell sh-4.1$ su Permission denied
I have rooted my phone successfully. I know this because I'm able to install apps on SD card and I have a program called SD Maid that is able to operate with root permissions.
You might need to activate adb root from the developer settings menu. If you run adb root from the cmd line you can get:
root access is disabled by system setting - enable in settings -> development options
root access is disabled by system setting - enable in settings -> development options Once you activate the root option (ADB only or Apps and ADB) adb will restart and you will be able to use root from the cmd line.