My data is only partially syncing

Usually means a sync was interrupted before completing. Trigger a manual sync (pull-to-refresh on iOS / Android, or ⌘S on Mac) and let it run all the way through. If the issue persists across multiple manual syncs:

1. On the device with the most up-to-date data, create a backup.
2. On that same device, go to Settings > Sync > Next Sync Action on iPhone, iPad, or Android, or 2Do > Settings > Sync > Next Sync Action on Mac.
3. Choose Replace server data, then trigger a manual sync and let it finish.
4. On each device that is missing data, choose Replace local data from Next Sync Action.
5. Trigger a manual sync on each out-of-sync device. This pulls the clean server copy down to that device.

Learn more in Replace server data or Replace local data?, Sync — Overview for Mac, Sync — Overview for iOS, or Sync — Overview for Android.