8 plus will charge on the factory mat after the charger upgrade but you must place it carefully and it can’t move. It Does sit at a slight angle. Helps to not have a case
JPC,, having same issue on a Tahoe. There is another conversation on this forum discussing it also. Search Iphone 8. I have contacted GM infotainment reps, and both dealers here. Nothing yet. I know the vehicle pad works as my friends Samsung charges fine even with a case. I set my Iphone 8 on a charging pad at Best Buy and also charges fine. Not sure whats next but very disappointed. I know the 8 just came out but GM and Apple must talk.