One article, with its sources
Sync failed
If the app shows "sync failed", first sign out and back in 1. Then check that the device sets its date and time automatically: a wrong clock is the most common cause since version 3.4 2. If it still fails, clear the app cache in Settings → Storage 1.
- 1Troubleshooting Guide v4, p. 12
- 2Release Notes 3.4