Generally, every project sharing a file always has the latest version of the file. When you check in the file in any project, all the projects are automatically updated. However, you can use the Pin button in the History of File dialog box to share an explicit version of a file. This message has the following cause and solution:
If you click No, the project shares the pinned version explicitly, and does not receive checked-in changes from other projects.
If you click Yes, the project returns to a sharing state in which it is always using the latest version of the file.