What are the complete specs of the system that this card is getting tested in? If the card has 6/8-pin PCIe power connectors on the side, are there corresponding cables from your power supply plugged into them, and does the power supply even have the capacity to run such a card?
Graphics Card 6-pin and 8-pin connectors Explained. Buy Adapters or Power Converter Cables for 6-pin PCI-E and 8-pin PCI-E connectors. 6-pin power connector can supply 75 Watt to the graphics card while 8-pin power connector can deliver maximum of 150W to your graphics card. A graphics card with...
graphicscardhub.com
And is the monitor plugged into the graphics card itself, or into a port on the motherboard?
It could be a fake card, or a defective card, but there's also a chance that it could simply not be hooked up properly. I will say that the price seems rather suspicious though, as I would not expect someone to sell a working Titan X for that price. Even if it's not a Titan X, maybe it could be a working lower-end card that still has at least some value though, even its less than what you paid.
Perhaps you could take some photos of the card. Does it have a backplate (like a Titan X Pascal) or a visible circuit board on back (Like the earlier Titan X)? If it's the earlier cooler design with no backplate, does the back of the card look like what's shown here, and are there any labels or anything on it?
https://legitreviews.com/wp-content/uploads/2015/03/geforce-gtx-titanx-back.jpg
If you have all the cables hooked up correctly and a suitable PSU, and still can't get it functioning in any way, then removing a bunch of screws to get the cooler off might be needed to get a better idea of what the card actually is.