Summary
UEFN session validation failing with download_failure 404 after power outage – module stuck in backend
Please select what you are reporting on:
Unreal Editor for Fortnite
What Type of Bug are you experiencing?
Other
Steps to Reproduce
- Open UEFN
- Open any project (including new blank projects)
- Click “Start Session”
- Wait for validation
- Session fails with MODULE VALIDATION FAILED and download_failure 404
Expected Result
UEFN should validate project modules successfully and launch the live session without backend validation errors.
Observed Result
The session fails during validation with:
FlowStep_ResolveSessionCandidates()
errors.com.epicgames.pre-processing.download_failure
Response code 404
The project cannot start a live session.
Platform(s)
pc
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Additional Notes
This issue started immediately after a power outage while I was in a live UEFN session.
Since then:
- The error persists for several days
- It affects all projects on my account
- Another Epic account works normally on the same PC
This strongly indicates a backend module corruption or a stuck Valkyrie validation state linked to my account.