Norton error 8505 129 is one of the most common errors encountered by users while trying to install or open the Norton antivirus software. 

On receiving this error code, you’ll be unable to open the Norton antivirus software and after a certain time, the system will freeze and crash. 

This error code mainly appears if the PST files are missing or corrupted. Most users have reported that they do not know how to solve this error code on the device. 

If you are also searching for the solutions to this particular error code, then this article will help you. Here, we will be explaining some of the solutions to get rid of this error code instantly.

Causes Behind Norton Error 8505 129

Below, we have listed some of the prominent causes responsible for this Norton error 8505 129.

  • Malware infection
  • Windows Firewall
  • Corrupted system file
  • Missing or corrupted the Norton antivirus application
  • An older version of the Operating System
  • Poor internet connection 

Now that you know the causes behind this error, you can perform the solutions listed below for an easy and quick fix. 

5 Solutions for Norton Error 8505 129

In this section, we are going to share five effective and quick solutions to fix the Norton error 8505 129 on the system. Try to perform the fixes exactly as instructed below.

Solution 1 – Check the Network Proxy Settings

Incorrect network proxy settings can cause this error code on the system. So, you need to correct it by following these steps:

  1. Press the Win + R buttons to launch the Run box, type inetcpl.cpl and then click on the OK option or hit the Enter button. 
  2. From the Internet Properties window, go to the Connections tab and click on the LAN settings option.
  3. On the Local Area Network settings window, unmark the ‘Use a proxy server for your LAN’ under the ‘Proxy server’ box and then select ‘Automatically detect settings.’
  4. After that, click on the Apply button and followed by the OK option.

Solution 2 – Configure Network Connection Settings 

One of the easy ways in which you can fix the Norton error 8505 129 is to configure the network connection settings correctly. To do that, follow the steps cited below.

  1. Launch the Control Panel window and double-click on the Network and Internet section.
  2. Click on the Network and Sharing Center button. 
  3. Select the ‘Change network adapter settings’ button on the left panel. Locate the internet connection that you are using and right-click on it. Select the Properties option.
  4. When the Properties window opens, double-click on the Internet Protocol Version 4 (TCP/IPV4) to open the Properties window.
  5. On the Internet Protocol Version 4 (TCP/IPV4) Properties window, type the following addresses:
    1. Preferred DNS server:
    2. Alternate DNS server:
  6. Click on the OK option to save the changes. 

Solution 3 – Update the Operating System

In order to prevent this error from occurring, it is important to keep the system up to date. Sometimes, an older version of the Operating System can also cause this error. So, you need to update the system properly. To do that, follow these steps as stated below:

  1. Right-click on the Windows icon and choose Settings.
  2. Go to the Update & Security section and select the Update tab.
  3. From the Update tab, click on the Check for updates option to find the updates. 
  4. If an update is present, you will get to see the Update button, click on it to begin the update process. 
  5. Once the update process is complete, restart the device and then check if the Norton security application opens properly without any error. 

Solution 4 – Turn Off the Windows Firewall

Sometimes, the Windows firewall can also be responsible for the Norton error 8505 129. So, you need to turn it off by following these steps:

  1. Go to Control Panel and select Windows Firewall.
  2. From the Windows Firewall window, click on the Turn Windows Firewall On and Off button on the left panel.
  3. On the right, mark on the Turn off Windows Firewall option from both Private Network settings and public Network Settings sections.
  4. After doing this, click on the OK option to save the changes. 

Solution 5 – Reinstall the Norton Antivirus Software

If the Norton antivirus software is corrupted then you may encounter this error code on your device. So, you can uninstall it and then install it again. Here are some steps that you can follow:

  1. Press the Windows button and move to Control Panel.
  2. Double-click on the Programs & Features section.
  3. Scroll down the page until you find the Norton Security software, select it. After that, click on the Uninstall button.
  4. Once the removal process is complete, reboot the device and then reinstall Norton. 
  5. So, visit the official website of the Norton security software and find the latest version of the Norton security software. 
  6. After finding it, install it correctly. 
  7. Once the installation process is complete, restart the system and then try to open the Norton antivirus application. 

Hopefully, following the above fixes will help you in fixing the Norton error 8505 129 easily. So, read this article carefully and perform the fixes one by one on your PC to get rid of this error from the device.