logicboard /MagSafe replace not working

If your new logic board isn’t working either, we face two scenaries, first is that you received a faulty replacement but that sounds a bit unlikely. The second is that you’re connecting one ore more faulty/shorted parts to your Mac that prevent startup. Your Mac will boot on it’s own just by plugging in magsafe and nothing else, thus I’d suggest disconnect everything from your board, including screen and battery and try if the board starts on its own without anything plugged in. If it does, board works and you’ll have to find the faulty part by plugging in all cables one by one until you find the culprit.