Why isn't my tablet turning on?

I had my tablet packed away when I moved and I recently found it. It was dead so I charged it for a little while but once I tried to turn it on it would not go past the screen that says Samsung in white letter and it keeps glowing blue behind it. I have tried a factory reset which didnt work. I can't figure out if I can remove the back or not. Next step is to take it to T-Mobile but I want to try and fix it myself first.