If you don't see Dropbox syncing icon overlays on your files, there are a few possible explanations.
The most likely explanation is that Dropbox may have shut down unexpectedly. Icon overlays appear over your files only when Dropbox is running. To check if Dropbox is running, look for the Dropbox icon in your menu bar or system tray:
If you've verified that Dropbox is running and are still having issues with icons, here are some other possible explanations:
If none of these scenarios apply, you may have a corrupted settings file. It's possible to fix your settings by unlinking and relinking your computer.
There are a few other operating system-specific explanations for why the overlays might not work on non-stock configurations of Dropbox:
Installing Dropbox without an administrative password will break all overlays. Re-installing using an administrator's password should resolve the issue.
If you have other applications or services that also add overlay icons or context menu items to the files within your Dropbox folder, try to temporarily quit them or uninstall them, and then restart Dropbox and Finder.
If the Dropbox overlays are in the first 15 positions, they will display; otherwise you'll need to make room for them. Please note that this requires you to delete or deprioritize other applications' overlays, so only proceed if you’re sure about what you'll affect.