Software & Apps Windows Connection Failed With Error 651: What It Is and How to Fix It A variety of causes could be behind your internet connection error by Brad Stephenson Freelance Contributor Brad Stephenson is a freelance tech and geek culture writer with 12+ years' experience. He writes about Windows 10, Xbox One, and cryptocurrency. our editorial process Facebook Twitter LinkedIn Brad Stephenson Updated on June 05, 2020 Windows The Ultimate Laptop Buying Guide Tweet Share Email The error 651 message is common on computers with Windows 10 through Windows 7 and usually appears in a small pop-up window. The actual text varies a bit, depending on the cause of the connection problem, but it always includes this text: Connection failed with error 651 Although annoying, error 651 is a relatively minor problem and shouldn't cause a computer to shut down, restart, or display the blue screen of death. Caymia / Getty Images Causes of a Connection Failed With Error 651 Error Error 651 indicates that an attempt at a connection to the internet was unsuccessful, or an existing connection has been terminated. A variety of issues can trigger the alert, from incorrect placement of an SYS file, erroneous modem setup, corrupted registry files, an IP address conflict, and driver problems to issues with your internet provider. How to Fix a Connection Failed With Error 651 Error Given the number of issues that can cause the Error 651 message, the approaches you can take to solve the problem are many. Here are a few things to try. Test the connection on another device. This is the easiest way to check if the problem is related to your Windows computer, modem, or service provider. If you can connect another device to the same Wi-Fi network, the problem lies with the computer. If you can't connect anything else to the same network, the problem is with the modem, router, or provider. Try a different connection. If you can't connect with another Wi-Fi network that you know is working, the problem is the computer. If you can, the connection is to blame. Check for loose cables. Make sure all of the power and connection cables are plugged in securely to the computer, modem, router, and wall. This might seem obvious, but connections come loose. Reboot the modem and router. Unplug both devices, wait a minute, then plug in both devices. This might take a few minutes. Restart the computer. This tech tip is a classic for a reason. It fixes a range of troubles, whether you use Windows 10, Windows 8.1, or Windows 7. Run the Internet Connections Troubleshooter. Open the Start Menu and select Settings > Update & Security > Troubleshoot > Internet Connections > Run the troubleshooter. Make sure the modem, router, and all associated cables are connected before running the Internet Connections Troubleshooter. Check for Windows updates. Go to Settings > Update & Security > Check for updates. The Windows update process installs the latest features and security updates. It also scans the computer, fixes errors, and downloads any files that may be missing or corrupted. Update the network adapter driver. Drivers help hardware run correctly. Installing a newer one, if available, could solve the internet connection problem. Disable antivirus software. Some antivirus software can prevent Windows computers from connecting to the internet. Pausing the antivirus program or turning it off completely frequently fixes internet connection issues. Try these Windows 10 command prompts. First, you'll need to open Command Prompt. In the Windows 10 taskbar search bar or from within Cortana, type Command prompt, then select Run as administrator > Yes. Next, type these command prompts, pressing Enter after each: netsh int ip reset reset.log This resets the Windows networking stack. Netsh interface tcp set global autotuning=disabled This disables autotuning. regsvr32 raspppoe.sys This re-registers the raspppoe.sys file. Restart the computer, and check the connection.