# UEFN fails to launch — "Failed to open descriptor file" + ICU crash (Release 41.20) 

**URL:** <https://forums.unrealengine.com/t/uefn-fails-to-launch-failed-to-open-descriptor-file-icu-crash-release-41-20/2736835>\
**Category:** Issues and Bug Reporting\
**Tags:** unreal-engine, unreal-editor-for-fortnite, crash, bug-report, editor\
**Created:** [July 19, 2026, 1:05pm UTC](https://forums.unrealengine.com/t/uefn-fails-to-launch-failed-to-open-descriptor-file-icu-crash-release-41-20/2736835 "2026-07-19T13:05:26Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![Jimbohalo10](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/jimbohalo10/32/961440_2.png) [@Jimbohalo10](https://forums.unrealengine.com/u/Jimbohalo10)\
**Post date:** [July 19, 2026, 6:59pm UTC](https://forums.unrealengine.com/t/uefn-fails-to-launch-failed-to-open-descriptor-file-icu-crash-release-41-20/2736835/2 "2026-07-19T18:59:21Z")

</div>

hi @Wuoli19

Please run verify on your installation.

[How to Verify Fortnite/UEFN](https://forums.unrealengine.com/t/urc-exe-and-urc-dll-get-flagged-as-malware-from-microsoft-defender/1802519/5)

If this still fails you might have to uninstall Fortnite/UEFN and reinstall as looks like some parts did not get installed correctly in the patch update

---

_[View the full topic](https://forums.unrealengine.com/t/uefn-fails-to-launch-failed-to-open-descriptor-file-icu-crash-release-41-20/2736835)._