Laptop Screen, Inverter Replaced

Hi, I’ve got a laptop here with what looks like a backlight that isn’t working (You could still see Windows faintly on it). Replacing the inverter, the backlight turns on at the Windows login screen, but nothing else is there.

Any ideas on what could be wrong? It still works with an external monitor so I _assume_ the graphics card is working correctly.

Would I be right in blaming the inverter? Or is this just wrong? I think so because the screen works without backlight with one inverter, and the backlight works with the new inverter…