Cook Errors when starting session in UEFN?

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

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.