The content area is empty. This area identifies what will be inserted when the part is reused. If the content area is empty, this part cannot be reused.
Explanation
A part diagram has two areas: a content area that is identified by a white background and a blue border surrounding it and a sandbox area that consists of everything outside the content area. Only the elements in the content area are considered to be in the part. Any elements in the sandbox area are ignored when reusing the part. If the content area is empty, you cannot reuse the part in other sketching artifacts.
User response
Add content to the part and then save it.