Chosen Solution
I recently removed the back glass from an iphone 8. Before putting on the new piece I tested the phone. After showing the apple logo it automaticaly shuts off. Does anybody know what could be going wrong?
Doing a back glass removal without emptying the housing is a recipe for disaster. So much could be wrong it’s hard to know where to start. I would start by testing a bare-bones setup. Start by disconnecting the battery first (always!). Then disconnect the digitizer, LCD, charging coil, front camera, rear camera and home button extension flex. Now re-connect the battery; you should only have the battery and Lightning Dock flex connected. Connect a known-good, preferably Apple-original Lightning cable to an iTunes enabled computer. Does iTunes recognize your phone? If so, then you should re-connect one flex at a time until the phone stops working. I would start with the charging coil, then the Home button flex, then add the rear camera, LCD & Digitizer. If the bare-bones setup does not get recognized by iTunes, then you most likely have a logic board issue. You could send it (or find a local) to a repair shop that specializes in micro-soldering repair.
