This error is caused by the work item in question not having the correct work item type set as its parent. Avion requires the following parent types:
For Features in Azure DevOps, the required parent type must be an Epic.
For User Stories / PBIs / Requirements in Azure DevOps, the required parent type must be a Feature.
Azure DevOps allow very loose relationships, which don't fit the structured approach that story maps require. Therefore, Avion insists on a more strict data model, ensuring that cards of a certain type always have the correct parent or child type.
Another potential cause of this error is the fact that a work item has a parent of valid type, but the parent is located in another area path.