First thing after a big repair would be to make sure everything is connected, after that you may want to try and reseat the connections as well if it still isn't working. I ran into a problem where the power button wasn't working after a trackpad repair and reseating the cable for this fixed it. Also an SMC reset can be tried as well.
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Ps. Remember to use electrostatic protection during computer repairs. If you don't have a wristband, make sure you are touching something metal during the whole repair.
First thing after a big repair would be to make sure everything is connected, after that you may want to try and reseat the connections as well if it still isn't working. I ran into a problem where the power button wasn't working after a trackpad repair and reseating the cable for this fixed it. Also an SMC reset can be tried as well.