The Invalid Structure is issued in the following situations:
<structure> must have at least one attribute: You have a structure with no attributes.
Add, at least, one attribute to your structure. How?
<structure>.<attribute> defines a recursive Structure data type definition: You have two or more structures with Record attributes that are using a recursive data type definition. For example, you have two structures: StructureA and StructureB. In StructureA, you have a Record attribute whose Record Definition is StructureB; and in StructureB, you have a Record attribute whose Record Definition is StructureA.
Edit these Record attributes and change their Record Definitions in order to avoid a recursive data type definition. How?
Structure Attributes | Error Messages