Screen backlight only after replacing motherboard

Hey folks! My Nexus 5 recently broke down and it seemed motherboard was damaged (i checked it via diagnostics tool). I replaced it and everything seems to be working fine, except screen is not showing anything. Weirdly, backlight is working! Phone itself is working too, I managed to unlock it and flashed latest firmware, but it didn't help. I also tried to reconnect screen flex cable, but it didn't help either. Any help will be much appreciated!

I attatch two photos of backlight working.

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