I get a permission error when placed layers are being synced - why?

If an Adobe document was created on a major later version of Adobe than the version you are opening it with (e.g. created on Adobe 17.X but opened with Adobe 16.X), and you then open it, you will see this popup:

If you proceed with the conversion, the metadata and relationships to IntelligenceBank placed files in the document may be entirely removed by Adobe. This can result in Permission error messages appearing on the document in lieu of the placed layers when trying to sync the document.

Unfortunately, this process is out of the control of the Connector. As such, it is essential that all users collaborating on a Document remain on the same major version of the software throughout the design process.