What to do when a connection error occurs on a Windows PC

Please try this procedure if your VPN connection is not working properly with the MillenVPN application you are using.

Install the latest version of the application

After uninstalling MillenVPN, download the latest version of MillenVPN and try connecting to the VPN again.
If you have already installed the latest version of the application, please reinstall it.
Click here to install the latest version of the Windows application.

(2) Re-login

Please click the second button from the bottom left of the MillenVPN application to log out and then log back in.

(iii) Protocol changes

Please change the VPN protocol to "WireGuard" or "OpenVPN" from the "VPN Protocol" item in the "Connection" tab of the MillenVPN application and try connecting again.

(4) Addition to exceptions

1. Open the "Windows Defender" item from the device's Control Panel and click on "Allow apps or features through the Windows Defender Firewall".
   
   
2. As shown in the image below, (1) click "Change Settings" or (2) click "Allow Other Apps", (3) browse to "MillenVPN Apps", and (4) click "Add".
   
   
3. MillenVPN " will be added to the list as shown in the image below. Check the box (5) and click "OK" (6).
   
   
4. Return to screen 1 and click on "Enable or Disable Windows Defender Firewall." The following screen will appear, check "Disable Windows Defender Firewall" and click "OK.
   

(5) Change settings for UDP ports 500 and 4500

1. Log in to MillenVPN and select Settings (gear symbol) from the left side menu.
   
2. CLICK ON THE "CONNECTIONS" TAB AND CHECK "VPN PROTOCOL".
   
3. Check your environment
   If the VPN protocol is set to "IKEv2" (default setting), please check if access to UDP ports 500 and 4500 is allowed by your firewall, security software or router settings. If not, please change the settings.

If any of the following applies to you, please change the protocol to "WireGuard" or "OpenVPN" and try connecting again according to the procedure for (2) Changing VPN Protocol.

• The above procedure does not solve the problem / It is difficult to change the setting
• Unable to change router settings OR unable to check availability of IKEv2 connection by another device.
• When connecting, "VPN Connection Failed The value cannot be null. Parameter name:device" error message is displayed.
  

(6) Reboot the terminal

This may be due to an internal error in the terminal. Please restart your Windows terminal and try the VPN connection again.

(7) Try other connection methods

If you do not see any improvement with the above steps 1) to 6), please check if you can connect with "MillenVPN Native" or "MillenVPN Native OpenConnect" by referring to the following page.

[How to get started with MillenVPN Native]
https://support.millenvpn.jp/669

[How to get started with MillenVPN Native OpenConnect]
https://support.millenvpn.jp/853

Note that if the " Unable to connect to the VPN server. " is occurring, it is likely that your environment is not configured to allow VPN connections. (If the error code is 809 or 87)
Please check if Windows Defender, firewalls between the client and server, security software, NAT, or routers are not configured to allow VPN connections.