It's unlikely that the trackpad received from iFixit is also faulty. I'd recommend check the screws directly beneath the trackpad in the bottom plate. Make sure the screws there are the correct screws - they should be shorter than the other bottom plate screws and if the incorrect screws are put in that place it could change trackpad functionality. Have you tried using an external mouse? If you are able to click with an external mouse, then the issue is most likely due to how the trackpad is installed or the trackpad cable connection. You may also want to try replacing the trackpad cable if you haven't already. Good luck!