If you cannot enable SLI on your x58 first test each card individually to ensure they are functioning poreperly on their own. If they both work fine, seat both cards in the motherboard, without the SLI bridge.Make sure both cards are recognized in the Nvidia Control Panel. If so, shut down the computer and attach the bridge. If SLI dissapears or causes a problem you will most likely need to replace the SLI bridge.

If both cards function properly individually, but you still cannot enable SLI in the NCP it maybe due to a conflict with your network driver. Please download the latest drivers for your video cards and network adapter here: https://www.evga.com/support/drivers/

After they both finish downloading first uninstall your network drivers, then the video card drivers. Reboot into safe mode by pressing F8 during POST. In Safe mode first install the network drivers, then the video card drivers. Reboot into windows normally and the option to enable SLI should be shown in the NCP.