I had a situation with a customer who had 2x 10GbE NICs in a Dell PowerEdge R720 server. The Network Adapters as seen below show "Not Present" It didn't seem to matter if there was a cable present or not.
We even tried disabling and re-enabling the adapter but this didn't help. A case was raised with Dell SST, first the NIC and the raiser was replaced. This did not fix it. We tried moving the Adpater to another slot and it worked, but to keep symmetry the customer wanted the adapter in this specific slot. Next Dell replaced the mainboard and CPU, this also did not fix the problem. We booted into a Linux liveCD and we could see that the NIC was functioning so this pointed to Windows.
The Deployment was using Windows 2012 R2 core mode so we could not use Windows Device Manager to see what was happening. I never seem to be able to get Device Manager working remotely. So I turned to DevManView which if free from NirSoft. What we noticed was that the card was listed twice. we tried disabling re-enabling the card but this didn't help. Fortunatly we can use DevManView to open the related Registry key. Because the nornal Administrator account doesn't have permission to remove device based reg keys, you can run RegEdit as the system account but using PsExec from Microsoft. We used DevManView to open the keys and delete them! Excercise caution here, know what you are doing with the registry and have backups, you have been warned!
The server was rebooted and the devices were re-detected and this corrected the problem!