Licensing checks are performed by a standard Unreal Engine module provided by Epic Games, known as PluginWarden. This module communicates with the Epic Games Launcher (EGL) to verify your entitlements on the remote Fab/UE Marketplace back-ends. In this section, we have compiled solutions for the most common issues related to this Unreal Engine module.

To ensure that PluginWarden can communicate effectively with the Epic Games Launcher (EGL), please make sure that:

• You are running the Epic Games Launcher (EGL) in the background (do not quit or terminate it).
• You are logged-in with the account that purchased the plugin (verify that the plugin is listed under Unreal Engine > Library > Library).
• The connection icon near your username is green, indicating that EGL is properly connected to Epic Games back-ends.
• You open your Unreal Engine project through EGL (from the Unreal Engine > Library > My Projects tab).

If the problem persists, try rebooting your PC to force EGL to refresh its local data and reconnect to the back-ends, then try again.

If the issue continues, please proceed to the next section.

Unreal Engine communicates with the Epic Games Launcher (EGL) using a standard plugin called UDP Messaging. Ensure this plugin is enabled for your project by following these steps:

• Open your project in the Unreal Engine editor.
• Go to the menu: Edit > Plugins.
• Search for and enable the UDP Messaging plugin.

After enabling the plugin, restart your project. If the issue remains, continue to the next section.

The system firewall may block communication between the Unreal Engine editor and the Epic Games Launcher (EGL). To quickly determine if this is the cause, temporarily disable your firewall:

• If you are using Windows Defender Firewall, follow Microsoft documentation on how to turn it on/off.
• If you are using another firewall product, please consult its documentation for instructions on how to disable it.

Restart your project; if the problem is resolved, re-enable your firewall and configure it to allow communication between the Unreal Engine editor and EGL:

• For Windows Defender Firewall, follow Microsoft documentation on how to allow an app through the firewall.
• For other firewall products, refer to their documentation to allow an app.

If the issue persists even with the firewall turned off, please restore the firewall and proceed to the next section.

The UDP Messaging module used by the Unreal Engine editor and the Epic Games Launcher (EGL) may encounter issues when Virtual Network Adapters (often used by VPN systems) are present. To determine if this is the case:

• Check your Unreal Engine project log (in the Unreal Engine editor: Window > Output Log; on disk: <PROJECT>\Saved\Logs\<PROJECT>.log);
• Look for a line similar to the following (your IP addresses and port numbers may differ):

  LogUdpMessaging: Initializing bridge on interface 0.0.0.0:0 to multicast group 230.0.0.1:6666.

• A normal output should indicate a successful binding and will look similar to:

  LogUdpMessaging: Initializing bridge on interface 0.0.0.0:0 to multicast group 230.0.0.1:6666.
  LogUdpMessaging: Display: Unicast socket bound to '0.0.0.0:64695'.
  LogUdpMessaging: Display: Added local interface '192.168.75.42' to multicast group '230.0.0.1:6666'

• In case of a failed binding, you may see an error message like:

  LogUdpMessaging: Initializing bridge on interface 192.168.1.124:0 to multicast group 230.0.0.1:6666.
  FUdpSocketBuilder: Failed to bind UdpMessageUnicastSocket to 192.168.1.124:0. Error code 21.
  LogUdpMessaging: Error: StartTransport failed to create unicast socket on 192.168.1.124:0

If your log contains a similar error, it indicates that another program (typically a Virtual Network Adapter or a VPN) is already using the necessary communication port, preventing the Unreal Engine editor from communicating with EGL. To resolve this issue, try the following:

• Disable other network adapters, especially virtual ones and any VPN connections.
• Disable and then re-enable the physical network adapters in use.

For more information and additional options, please refer to FUdpSocketBuilder errors causing frame rate drops but no networking in project.

If the issue still persists, you will need to collect several log files to share with Epic Games for further investigation:

• Open the Epic Games Launcher (EGL).
• Got to Settings and enable Enable Debug Logging.
• Select “Restart” when EGL prompts you to enable debug logging.
• Once EGL restarts, open your Unreal Engine project from the Unreal Engine > Library > My Projects tab.
• Use your project until the error or warning dialog appears.
• Close Unreal Engine.
• In EGL, select Settings, then Show Logs.
• Create a ZIP archive of the directory that appears.
• Create another ZIP archive of your project log directory:
  • under Windows: at <PROJECT>\Saved\Logs\
  • under macOS (for more details read Modernized Xcode Workflow - Access Logs):
    • If Sandbox is enabled:
      • Running through xcode: ~/Library/Logs/[project name]
      • Running by double-clicking or by using terminal: ~/Library/Containers/[your app's bundle ID]/Data/Library/Logs
    • With Sandbox disabled: ~/Library/Logs/[project name]
• Share these ZIP archives with support.

If the issue cannot be resolved — since the problem lies between Epic Games' components (PluginWarden failing to connect to EGL, and/or EGL failing to validate your purchase with the Fab/UE Marketplace back-ends) — please contact Fab/UE Marketplace Support by Epic Games (Fab Support, UE Marketplace Support) and report that PluginWarden fails to validate your purchase. Be sure to provide the collected ZIP archives.