Hey , first of all are you sure you have a fully working screen and did you get it from ebay ? if you didnt get it from there and the screens official you could be having back light issues .
hey guys please try this , Samsung Galaxy Tab S2 (Android) Press and hold Volume up, Home and Power buttons untilthe Samsunglogo appears on the screen, then release the buttons. The start-up screen will be briefly displayed, before thehard resetmenu appears. Press the Power button.