I'm having an identical issue to an earlier user. That user had not originally assumed root (run "su"). In my case I've tried everything but can't get su to take, based on the instructions here.
Here are my details:
* G Pad 8.3 Model# VK810 (Verizon VZW)
* Running 4.2.2(JDQ39B) - I have not accepted any OTA updates
* USB Debugging Enabled, USB > Internet > Ethernet Connection Enabled
* Successfully connects and shows devices with the ADB DEVICES command
I have no problem with any of the adb commands, I am able to push both files, change permissions, etc.
The only thing I cannot do is invoke SU, I get:
/system/bin/sh: su: not found
Because I don't have superuser privileges, I then get this error when attempting to run the loki_flash:
./loki_flash recovery /data/local/tmp/twrp.lok
[+] loki_flash v2.1
[-] Failed to open aboot for reading.
All adb commands are working great, I can move around directories, etc. I just can't run su.
Thank you in advance for any insight!