If this is from eBay, not that as I seller I like it when people do that, but you can go back and tell them that it's not as described, and you'll probably win the case. With that said, try working it out with your seller first and see if you can maybe get a partial refund if you don't want to ship it back.
If both the internal keyboard and trackpad are not working, it's possible the entire circuit isn't getting power properly. I had the same machine a few years ago and the backlight for the keyboard quit, and that's a seperate DC-DC step up boost converter that I didn't bother to troubleshoot because it was just a keyboard backlight I didn't need.
Perhaps start by measuring carefully for voltage on the keyboard connection. If reseating and a new keyboard(most likely not findable easily) don't solve this issue, there's probably some motherboard repair to be done.