Steam game will not launch under main user, only alternate user

[Windows 11]

I am experiencing a problem launching Fallout 3 from my Steam library on my Windows 11 Pro system, version 23H2, with an NVIDIA GeForce RTX 2070 Super. All other games in my Steam library launch and run correctly. When I launch Fallout 3, it stops immediately without displaying an error message. Importantly, I contacted Bethesda support, and they assisted me in creating an alternate user account. Fallout 3 launches and runs successfully under this alternate account. This strongly suggests a problem specific to my primary user account's configuration or permissions.

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