What Can I do to install the Barometric Vent

Hi this is very technical and nobody will probably be able to answer this anyway, but I am trying to install the iphone 8 plus barometric vent. I have a multimeter to measure the screws and they are the right sizes (only like .05mm off). So once I have measured my screws and press the vent right over the screw holes (making sure it stays in place), I place the screw and start screwing except the screw just keeps turning and not biting into anything. It does not even seem like it is able to get in the actual screw hole. To anyone who is a professional and does this on a daily basis, is there something I am doing wrong or something I should know? thanks a lot in advance!