Chosen Solution
Hello! I just replaced the battery of a iphone 8. After plugging the phone in it started once, turned off again and started bootlooping. Using an amp meter I noticed it ranged everywhere from 0.0 amps to 1.0. This behaviour still exists after swapping back to the old battery.
Something has probably been damaged when removing the old battery. Check around the charge connector for missing components. Also check the connectors for dirt then make sure you reseat all the connectors. Also connect everything except the ear speaker ribbon and try turning it on. If it turns on the ear speaker flex is damaged.
