Replaced screen, back screen, battery, and no sign of life

Hey guys! Looking for any ideas as to what could be the issue or any tips to look for , I got a dead iPhone 14plus, the battery had gone and screen was mucked said the seller. So I don’t know the history of the phone, but I e replaced the battery , the screen, the back glass including the wireless charger, and the phone shows no sign of life. Plugged into computer and computer isn’t detecting it’s even plugged in. Plug into wall and nothing, the phone just stays black with no sign of life. And ideas ? Thanks in advance !