Subfolder not sync'ed

Some subfolders (inside folders that are correctly synchnnoized) are not synchronized and I do not understand why. When I try to add the folder from my Windows 7 Explorer window a popup appears saying "Could not link to ". Any clue or suggestion, pelase?

Hi there, are these folders found in multiple locations? Google Drive has a feature that allows you to put a single folder or file in multiple locations. In this case, Insync only reflects syncing of one of these locations to avoid duplication.