The network card (PCI express card with 2 RJ-45 ports) in an RP5810 ScanStation displays flashing LEDs but is not visible in Windows Device Manager. The network ports will light up, and the ports are active. This card has a barrel connector for power in addition to the two network ports, identified as the old card in the photo below.
The old model NIC has the 8111E chip, which has limited compatibility with the RP 5810.
There are two half-height PCI-Express slots on the mainboard of the RP5810. See second photo below. If using the older model NIC, place in the PCI-Express x16 slot, which is black and terminates in a flexible tab near the CMOS/RTC battery. Do not use the full-length PCI-Express x4 slot, which is white in color and does not terminate in a tab.
The newer card (without the power connectors) work equally well in either slot.