Fix VPN Error 691 on Windows 10

A Virtual Private Network (VPN) is an important online tool that helps in enhancing your online privacy and security. Although VPN tools are great, it comes with its own set of problems which can cause lost VPN connections and error messages. Several users reported Connection failed with VPN Error 691. This can be a hindrance when you want to use a VPN, luckily there are few ways in which you can independently solve this issue.

VPN Error 691

The remote connection was denied because the user name and password combination you provided is not recognized, or the selected authentication protocol you selected is not permitted on the remote access server.

The VPN Error 691 is a Dial-Up error that occurs even when the connection you have is not a Dial-Up. This error can occur when the settings aren’t correct on the client or the server device and it cannot confirm the authenticity of the connection. The most common cause of Error 691 is an incorrect username or password. Sometimes it may also occur when you are using a Public VPN and attempting to login to the VPN with a domain that isn’t allowed, or domains are not allowed at all, or the security protocols required mismatch.

Normally, VPN error 691 occurs when there are problems with network protocol settings, remote access permission issues, firewall blocks, connectivity issues, etc. The most prominent causes can be clubbed as below:

  1. Incorrect Username and Password
  2. Incorrect connection security settings
  3. Problems with Networking settings

Fix VPN Error 691

Here are a few options that will help you troubleshoot VPN error 691

  1. Verify the logon ID and password are correct
  2. Use Microsoft CHAP Version 2
  3. Uncheck ‘Include Windows logon domain’ option
  4. Check connection’s security settings
  5. Change the LANMAN parameters.

Let’s look at these options in detail:

Option 1 – Verify the logon ID and password are correct

This might sound like a basic fix but works in most of the cases. Sometimes a VPN Connection failed with error 691 message appears when your username or password isn’t correct. To guarantee that your password is correct, we advise you to use the Show Password option and also check if you mistakenly have CAPS LOCK option turned on.

Option 2 – Use Microsoft CHAP Version 2

Sometimes, to fix error 691 you may need to use Microsoft CHAP Version 2; since VPN uses different protocols.  You can use it by following these steps:

1] Press ‘Win Key + X’ to open the Windows Menu

2] Select ‘Network Connections

3] Once the window opens, identify your ‘VPN connection’, ‘right-click’ and select ‘Properties’ from the menu

4] Click on the ‘Security’ tab

5] Select ‘Allow these protocols’ and check ‘Microsoft CHAP Version 2 (MS-CHAP v2)

6] Save changes by hitting ‘OK

After permitting Microsoft CHAP Version 2, check if VPN Error 691 still appears.

Option 3 – Uncheck ‘Include Windows logon domain’ option

This fix works if your VPN connection isn’t configured properly. Here you will need to disable the ‘Include Windows logon domain’ in your network connection properties. To fix the issue, follow the below steps:

1] Press ‘Win Key + X’ to open the Windows Menu

2] Select ‘Network Connections

3] In ‘Network Connections’ locate your VPN connection, right-click it and select ‘Properties

4] Click the ‘Options’ tab and uncheck ‘Include Windows logon domain’ option

5] Save changes by clicking ‘Ok’

Option 4 – Check connection’s security settings

The VPN Error 691 can appear if your connections security settings are not configured properly. To fix this issue, follow these steps:

1] Press ‘Win Key + X’ to open the Windows Menu

2] Select ‘Network Connections

3] In ‘Network Connections’ locate your VPN connection, right-click it and select ‘Properties

4] Navigate to the ‘Security’ tab and check that the Typical (recommended settings) options are selected

5] In ‘Validate my identity as follows’ section ensure the ‘Allow unsecured password’ option is selected

6] Click on the ‘Options’ tab and uncheck ‘Include Windows logon domain’ option

7] To save changes click ‘Ok

Now check if the problem is resolved.

Option 5 – Change the LANMAN parameters

Many users confirmed, changing LANMAN parameters helped in fixing error 691. This is fairly simple, follow these steps:

1] Hold the ‘Win Key’ and press ‘R

2] In the Run Dialog, type ‘gpedit.msc’ and click ‘OK’; this will start the Local Group Policy Editor

3] In the left pane, follow this path – Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options

4] In the right pane locate and double click ‘Network security: LAN Manager authentication level

5] Click ‘Local Security Settings’ tab and select ‘Send LM & NTLM responses’ from the drop-down menu

6] To save changes ‘OK’ and ‘Apply

7] Now, double-click ‘Network Security: Minimum Session Security for NTLM SSP

8] Disable ‘Require 128-bit encryption’ and enable ‘Require NTLMv2 session security’ option

9] Click ‘Apply’ and ‘OK’ and save these changes

Now, restart your PC to apply these changes and check if the issue is fixed.

Having any VPN error popping up and restricting you in connecting to the internet can be extremely frustrating. If VPN error 691 has been exasperating you, we recommend you to try some of our solutions.

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Ankit Gupta is a writer by profession and has more than 7 years of global writing experience on technology and other areas. He follows technological developments and likes to write about Windows & IT security. He has a deep liking for wild life and has written a book on Top Tiger Parks of India.