Numerous users have been confronted with the wow51900309 message. In this article, we will try to explore some possible solution to this issue. You can fix the wow51900309 error in World of Warcraft with any of these 4 methods. Continue reading to find out how. Method 1: Flushing Domain Name Server(DNS). You need to open an administrative command prompt windows. In Windows 8 and windows 10, to do so, Press Win+C in combination to bring up the ‘Charms bar’. In its search box, type cmd. Then, right-click on it and choose ‘Run as administrator’ option. Alternatively, you can also open an elevated command prompt from the WinX menu. Next, type the following and hit enter: ipconfig /flushdns You should be able to see a confirmation dialog window: Windows IP Configuration. Successfully flushed the DNS Resolver Cache. That is it, Now close command prompt window and try to Login again. This time, you should be able to log in seamlessly without wow51900309 error. Method 2: Using Google's DNS From Control Panel, you can change the DNS settings on your Windows 10 by taking the following steps 1. Go to Control Panel. Click on Network and Internet. Click on the Network and Sharing Center tab. 2. Click on Change Adapter Settings on the left pane. 3. Right-click the network interface of the internet connection, then select properties. 4. From the list, select Internet Protocol Version 4 (TCP/Pv4). 5. Click the properties tab. 6. Click the option "Use the following DNS addresses." 7. Input your preferred and alternate DNS server addresses. You can input any DNS of choice here, including free DNS' like Google Public DNS and OpenDNS. 8. Google Public DNS addresses: 18.104.22.168 and 22.214.171.124 OpenDNS addresses: 126.96.36.199 and 188.8.131.52 9. Click the OK button. 10. Click Close to apply the new DNS settings to the adapter. Once you complete this process, your PC will start using the new DNS settings immediately. Method 3: Reset your Network (for Windows 10) After troubleshooting your system without success, try to reset your network. To do this, go to Windows Setting by pressing the Windows+i button on the keyboard, or clicking Start and then Settings button. This will take you to the Windows Settings screen, then click “Network & Internet.” 1. On the “Network & Internet” screen, click the "Status" tab on the left. Scroll down and click the "Network Reset" link on the right-hand side. 2. The "Network Reset" page shows a warning about the consequence of resetting your network, and also tells you a restart is required after the reset. Reset the network by clicking the "Reset now" button, and then reboot the system. 3. When the prompt to confirm network reset is displayed, click "Yes." 4. And that's all! After your system has rebooted, Windows will guide you through your network setup. Method 4: Configuring Router and Firewall Ports Most proxy servers, firewalls, and other Internet connection methods can restrict port access. Your configuration may be restricting packets from unknown sources. Make sure you have the following ports set up: TCP and UDP ports: 3724, 1119, 6012 In Windows 10: 1. Click Start. 2. Type Firewall and press Enter. 3. Click Advanced Settings. 4. On the left frame, click Inbound Rules. 5. On the right frame, click New Rule... 6. Select the Port radio button and click Next. 7. Select the TCP radio button. 8. In the Specific Local Port field, enter 3724. Click Next. 9. Select the Allow the connection radio button. Click Next. 10. Make sure Domain, Public, and Private boxes are all checked. Click Next. 11. Enter any name for this rule. Click Finish. Repeat the steps above for each port you need opened based on the above table. Your firewall should now allow traffic on the necessary ports for proper Blizzard Downloader operation.