Rainbow Six Siege's error code 8-0x00003700 typically indicates problems with game server connectivity, corrupted game files, network issues, or interference from antivirus/firewall software. To fix it:
• Check Game Server Status: Determine the official status of the Rainbow Six Siege servers. If there are any current server issues, you may need to wait until they are resolved.
• Ensure Internet Connection: Make sure your internet connection is stable and operational. Check to see if any other online services are functioning normally.
• Restart the Game or PC: Close and relaunch Rainbow Six Siege. Alternatively, you can restart your computer to get a fresh start.
• Check for Game Updates: Use the game launcher to look for any available Rainbow Six Siege updates. Install them if there are any pending updates, as they may include fixes for known issues.
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Unable to Launch Rainbow Six on Epic Games

I bought Rainbow Six from Epic Games and downloaded the game. Whenever I attempt to launch it through Epic Games, I'm redirected to Ubisoft and encounter an error message informing me that an Epic Games service is presently inaccessible. Whenever I try to launch the game directly from its files, it ...