I had bought an extra iPhone SE and kept it in its box as a replacement for my wife’s when it was looking like small iPhones were disappearing (Model A1662). I sent it in for a trade in for a new iPhone for Xmas recently and though they originally offered me money, when it went to the reseller for check, they offered me $0.
When I got it back, I found that it would not charge up, just cycling from a start up Apple screen, powering off and doing that ad nauseam. Forced power off does not help.
Is there a trick to fixing this or resetting the system from my Mac when connected. Is there a software that will let me access it and fix the problem so I can get it functioning for resale?