Let me ask for some clarity. Did you just remove the normal back that protects the battery, sim card and sd card? Or did you being to take the phone apart?
Have you tried
Try a restart:
Press and HOLD both Vol Up/Down buttons. Keep holding while the screen goes fully black (ignore the screenshot), keep holding through the Black/White logo and when the Colored Logo shows up, release those buttons.
If you have the STL100-1 variant the volume button reset method doesn't work. In that case, Press and HOLD the Power On Button until you see the LOGO as above