I lost all my data during sync with Dropbox. Can I still restore my data?

If you have two or more devices syncing with Dropbox and believe one of the device still contains the most up-to-date data, please launch 2Do on that device and under Sync Settings select ’Replace Server Data’ from the ’Next Sync Action’ setting. On the Mac this is under Preferences > Sync > Sync Options. On the iPhone this is under Settings > Sync > Next Sync Action. Press Sync to replace data present in Dropbox.

This will replace everything in Dropbox. You can now launch 2Do on your other devices and select ’Replace Local Data’ from under Next Sync Action and then Sync. This should restore everything on your other devices.

Please read instructions given here