Chosen Solution
So I received this device that wouldn’t charge or show the apple logo, I had first replaced the lightning port, found that wasn’t the cause and then replaced the battery. After that the device worked and charged just fine and I gave it back. A few days later the same issue came back. I tried disconnecting the battery and reconnecting, then using my charger, still no go. Could this be an issue with their charger killing batteries, a faulty board, or something entirely else?
If you have a Dcps or another iP7 try charging the apparently dead battery a little bit, even a 5% would suffice, then put it back into your phone. If it will start charging that would rule out a bad battery and confirm you would have a board issue. A partly charged and a drained battery may show different behavior with a board issue.
If you can transfer the logic board to a know good know working iPhone 7 plus and see if it works if not then you have an issue with the logic board. if it is ok then you have an issue(s) with the battery charging dock connector
