# Cook Errors when starting session in UEFN?

**URL:** <https://forums.unrealengine.com/t/cook-errors-when-starting-session-in-uefn/2484114>\
**Category:** Issues and Bug Reporting\
**Tags:** fortnite-creative, unreal-editor-for-fortnite, bug-report, editor, fortnite, Cooking-Failed\
**Created:** [April 30, 2025, 9:23pm UTC](https://forums.unrealengine.com/t/cook-errors-when-starting-session-in-uefn/2484114 "2025-04-30T21:23:39Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Spigon6](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Spigon6](https://forums.unrealengine.com/u/Spigon6)\
**Post date:** [April 30, 2025, 9:23pm UTC](https://forums.unrealengine.com/t/cook-errors-when-starting-session-in-uefn/2484114/1 "2025-04-30T21:23:40Z")

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### Summary

HI, working on a map in UEFN, and every time I try to start a session, I get the following errors;

We hit an error while cooking this content  
errors.com.epicgames.content-service.cook\_failure  
CookJobId:ab5ba464-3aac-4cf4-9d80-76bfe93aa542  
An error occurred while communicating with the game servers (failed to cook module 26b244a4-4c21-f387-432a-80a415246c0c (artifact 0bc3e812-e400-4a0e-a59a-5d1c2e3cca56:pc) (cookJobId ab5ba464-3aac-4cf4-9d80-76bfe93aa542) with error code errors.com.epicgames.cookplugin.assetvalidationerror).

I have no idea how to trace this… Any help?

### Please select what you are reporting on:

Unreal Editor for Fortnite

### What Type of Bug are you experiencing?

Other

### Steps to Reproduce

not sure…

### Expected Result

assets cook and edit session starts

### Observed Result

cook error appears, edit session never starts

### Platform(s)

pc

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<div class="post-metadata">

**Author:** ![Spigon6](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Spigon6](https://forums.unrealengine.com/u/Spigon6)\
**Post date:** [April 30, 2025, 10:15pm UTC](https://forums.unrealengine.com/t/cook-errors-when-starting-session-in-uefn/2484114/2 "2025-04-30T22:15:51Z")

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I have NO CLUE what I did that fixed it but–

removed newest device creations  
reverted to recent revision upload, then reverted back

it worked.

magic.

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**Author:** ![system](https://d3kjluh73b9h9o.cloudfront.net/original/4X/7/1/3/713c9d3f58553f0de89543d76a8a3a2779dc9fa4.png) [@system](https://forums.unrealengine.com/u/system)\
**Post date:** [October 27, 2025, 9:23pm UTC](https://forums.unrealengine.com/t/cook-errors-when-starting-session-in-uefn/2484114/3 "2025-10-27T21:23:45Z")

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