Fix: “The Realtek Network Adapter was not found. If Deep Sleep Mode is enabled…”

The fastest, most reliable fix is a full power drain reset. Do this first, then try BIOS and driver steps below.

If the adapter is still missing

1) Make sure onboard LAN is enabled in BIOS/UEFI

Reboot and enter BIOS/UEFI (Del/F2, varies by vendor).
Find Onboard LAN / Integrated NIC / Ethernet Controller and ensure it’s Enabled.
Save & exit, boot back to Windows.

2) Clean driver reinstall

Open Device Manager. If you see the Realtek adapter (or an unknown NIC), right-click → Uninstall device → tick Delete the driver software for this device → OK.
From the motherboard / PC vendor support page, download the latest Realtek PCIe GbE or 2.5GbE LAN driver for your exact model and Windows version.
Install and reboot.

3) Reset Windows network stack

Run these in an elevated PowerShell or Command Prompt (right-click → Run as administrator), then reboot:

netsh winsock reset
netsh int ip reset
ipconfig /flushdns
shutdown /r /t 0

4) Still nothing? Likely hardware

If the NIC never reappears in Device Manager after the power drain + BIOS check, the onboard Ethernet chipset may have failed. The practical workaround is a USB-to-Ethernet adapter (plug-and-play) or a cheap PCIe Ethernet card for desktops.

FAQ

What is “Deep Sleep Mode” on Realtek NICs?

It's a low-power state the controller can get stuck in after certain power events. Fully removing power and discharging the board with a 30–60s power-button hold clears it.

Does Fast Startup affect this?

Yes. Fast Startup is like a hybrid hibernate and can preserve the stuck state. If the issue returns, disable it in Control Panel → Power Options → Choose what the power buttons do → Change settings that are currently unavailable → uncheck “Turn on fast startup”.