Same issue here on ++Fortnite+Release-42.30-CL-58813929 (Windows 11). UEFN dies 2-3 s after launch with “Failed to open descriptor file ../../../FortniteGame/FortniteGame.uproject”. Reinstalling UEFN, verifying, and Defender exclusions do not help.
I think I found the cause in the launcher log. Every time UEFN (Fortnite_Studio) is installed or verified:
LogEoshPatcher: Warning: StartTask: BinaryId [fn:1e8bda5cfbb641b9a9aea8bd62285f73:Fortnite_Studio:++Fortnite+Release-42.30-CL-58813929-Windows] — dropped 2 stale DesiredComponents: [A17316661F902216B15E8DAB34ECCD71,BC27D46CFC5347479B3F118F9A31EA06]
LogEoshPatcher: StartTask: … — using default components:
LogEoshPatcher: StartTask: … — resolved tags:
Those two component IDs are the Fortnite base game’s InstallComponents (from its .item manifest in ProgramData\Epic\EpicGamesLauncher\Data\Manifests). The Fortnite_Studio .item ends up with “InstallComponents”: and an empty “ManifestHash”. So UEFN gets installed with no editor content, which explains the missing descriptor and why no UEFN log is written.
Looks like a launcher/EOSH patcher issue: Fortnite_Studio inherits the main app’s components, then drops them as stale. Hope this helps FORT-1152398.