Chosen Solution
Repair failed. iPhone 8 will not power up. I took it to a professional repair facility who confirmed I had done everything correctly. They swapped out the display and the battery but the iPhone is still dead. Unfortunately, I forgot to back it up before replacing the battery so all photos are lost :( Any suggestions will be appreciated.
If it still will not power up after trying with a new battery and/or a new display it sounds like something happened in the course of repair regarding the logic board. Are you sure it’s not powering on at all (vs it powers, but nothing is appearing on screen)? I would connect it to a computer or a USB Ammeter to see if it can be detected, or if it is consuming any current. What sort of tools did you use to detach the battery and/or the display? It is not uncommon for pry damage around connectors to dislodge components in that area and it can be difficult to detect without a microscope. Additionally many of these components are covered by foam stickers or a covering to prevent the components from liquid contact/damage. If this is the case they are still repairable, but not every repair shop has someone on staff who can do board level repairs. You would need to find someone who has microsoldering skills. In which case the board could be resurrected and your data should still be intact.
