Games for Windows Live was a digital distribution platform developed by Microsoft. Since 2013, the company has gradually phased out its support, and the whole thing is now dead. However, there are still titles that are associated with it - until yesterday, Fallout 3: Game of the Year Edition was one of them. That's when an update numbered 18.104.22.168 was released on PC, which cuts the game off from the now-defunct service.
Keep in mind that with this patch, the compiler was changed to Visual Studio 2019. As a result of this move mods for Fallout 3 will stop working.
- Fallout 3 - game guide