Star 5230 blank display

I newbie with this but I change the broken display of my star 5230 and when I turned it on, the display lights on a dark screen. But it seems to work cause if you touch the screen it shakes. If you press the block button the screen gets darker and then turns of. If you press it again, the screen turns on but blackened. I can call it, it shakes and receives, I can talk with another device.

What I have done wrong?

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It sounds like the connection that actually lights up the screen isn't quite right.