Root a Samsung Galaxy 4 tab 7", Kies isn't working
Flash your stock ROM using Odin whilst your device is in
Download mode  Power  +  Volume Down  +  Home 

(Put the file in the AP/PDA depending on what version of Odin you have). If this works then your tablet may be back to factory state, but if it fails then you have Hard bricked your tablet. Presuming it isnt bricked, use the latest .apk file of King Root to root your Sm-T230. 

Stock Rom Download from XDA forums: ACHERON ROM v2.1.1 and
Odin 3 download