Error Unknown Cook Failure


I’m pretty new to UE4 and after following a tutorial i’m having issues with packaging the end content, wondering if anyone can help and point me to where the issue may be!

link text

There is an error in the log:

LogProperty:Error: UStructProperty::Serialize Loading: Property ‘StructProperty /Game/FirstPersonBP/Blueprints/GameBlueprints/BP_MasterItem.BP_MasterItem_C:ItemData’. Unknown structure.

Maybe BP_MasterItem is referencing ItemData, but ItemData is a struct that no longer exists.