The feature class to sync does not have attachments enabled. I'd be happy to explore my device and provide error details.
The fields that have have for this feature class are MEDIA_ID, COMMENTS, HYPERLINK, SHAPE, created_user, created_date, last_edited_user, last_edited_date, GlobalID, OBJECTID
It is archived and has globalid's it is not nested within a feature dataset. It resides at the geodatabase root. It is not z-aware and the coordinate system is NAD83 LAT LONG.