It is probably the first thing you need to check if you are getting synchronization issues with Dropbox. For obvious reasons, Dropbox requires a valid internet connection to synchronize files.

Dropbox is adding a suite of features to its file-hosting services to provide more syncing tools for app developers and make it easier for end users to access their data across devices. The changes, ...

Replacing Dropbox with Syncthing, for most users, will feel like a drop-in replacement as long as you know exactly what you're looking for in a tool.