iPhone15 pro max screen replacement not working; reset and power cycling still black screen

You have to have special firmware that’s required for the screen to operate properly. But beside that, the screen should not be black. This sounds more like a defective screen. But a home repair without the proper firmware/software will not perform to the same specs as the original equipment screen.

Did you buy the screen from Apple directly? iPhone 15 Pro Max, does qualify for Apple Self-Service, IF you buy the screen and parts you need to replace the screen directly from Apple. If you bought an aftermarket screen and you disassembled your iPhone, we can't help you. And Apple won't help you as this would be unauthorized tampering to your iPhone.

If you bought a 3rd party screen, you can take your phone to an iFixit type shop and hope they can help you. But if you damaged the phone, it will buy a new iPhone time.

I don’t know what to tell you. You opened up the iPhone so no warranty even if you purchased AppleCare. Your water resistance is gone and you have a screen that doesn’t work. My gut tells me that it’s a screen issue, but you can wait it out for a software update. Sorry, I’m at a loss to go much further. Best of luck with your issue.

GeneVTGrad wrote:

Ok, for all the people that know an answer other than you're screwed, how can a mainboard or screen be tested to verify basic function? Incidentally, I didn't open the phone. Another person that can't afford $500 for Apple to fix the device had a cell phone shop do it. I'm not asking for Apple warranty help, trying to help a family member as an electrical engineer with direct experience in microelectronics.

Take the phone to an iFixit type shop and see if they can test it. Your issue is really out of the realm of what just about everyone here can offer you.