Post Backlit mod:why does my Gameboy turn on and off quickly?

I bought a custom painted SNES GBA shell with motherboard and 32 pin ribbon adapter already connected. Insides already trimmed for screen so all I need to do is install AGS 101 screen. I take it apart to put screen in. After putting in everything together. I put some brand new batteries from my other GBA to test it but it will not stay on. I switch the power button to ON position, the green light comes on for a split second then turns off immediately after. The screen does not have a reaction. Just stays completely off. Black no power. Did I do something wrong? I opened it up and flipped the white tab but that didn't work either. Did I break the ribbon cable? Help please. Thanks!