If the source, or destination, is set to use a DFS share, e.g. \\servername\DFS\, then it may not find any sub-folders in the share. This is due to the way DFS works. Each sub-folder is actually a junction point and not a standard folder. By default SyncBack will ignore junction points. To stop SyncBack from ignoring junction points: modify the profile, switch to Expert mode, go to:
Compare Options > Attributes

page and untick the option for:
Ignore NTFS junction points (reparse points)