DS Lite powers on but no display

I recently bought some broken DS Lites. One of them powers on with the green light staying illuminated, but the top and bottom screen both stay blank. I swapped the mother board with a known good one and the system works, which shows me both screens are good. when I put the original motherboard back in it still powers on but blank screens. I have tested the wifi card and it is good. F1 and F2 have continuity. Now visible corrosion as the motherboard looks very very clean. I put some pressure on the chip under the cartridge slot and nothing changed. Really have no idea what the issue could be. Any thoughts?