|If it's not showing up in DM at all, then your NIC could be no good. I would test by reseating it.|
If it's a desktop PC I would first unplug the power, then I would open the box and while grounding myself on the case (have your forearm touching it is good enough) I would then remove the card and reseat it firmly into the slot.
Leaving the case open at this time, I would then plug the power back in and boot up and check DM. If the network interface appears, then that was all the issue was and you can now close up your case and proceed to install the correct drivers.
If it doesn't show up in DM, then you either have a bad card, or a bad slot. The simplest thing to do in that case is try the card in another slot (assuming you have another free one). If it still doesn't work, then it has to be a bad NIC (network interface card).
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.