It cannot be charged and cannot power up, what's wrong with it?

Hi, I have a Samsung Galaxy Note 2 GT-N1705. It cannot be power charged. The battery is inside the battery compartment and with the charging cable plugged into the USB Charging Port charging, the screen does not show up anything. Before it used to show a green charging indicator in Samsung phones while the power cable is charging, now it does not show up anything at all. And it cannot be powered up when I depress the Power on/off button on the phone.

So I tried charging the Battery using another battery charger and after the battery has been charged, l put the battery inside Samsung Note 2 and try to power up depressing the power on/off switch. It also cannot be powered on. Tried using a Brand New Battery also cannot boot up and power on. Some Technicians told me it is the USB Charging Port problems and some said it is the Motherboard problems.

So I just puzzled over what is the main problem and what faulty hardware need to be replaced? Is it USB Charging Port Flex mic cable replacement parts or motherboard replacement parts? Thanks please advice.

Eric Xutrilla