Hello,
Are you sure, that Dropbox connection is possible from both, your iPhone and your desktop?
ThinkingRock Desktop has to be running at the moment you do the Synch.
I suggest to do the following.
1. Test Dropbox connection on your desktop
2. Test Dropbox connection on your iPhone
3. Run ThinkingRock on your desktop and verify, that the correct Dropbox directory is configured in the settings.
4. Run the iPhone app and initiate the Synch process.
This should work.
Please let us know if it is working now.
Best regards,
Benjamin