If you get message stating you haven't backed up in several days, there are a few simple things you can do to check the current status of your backup and to get it working again.
1. Restart your computer.
2. Launch Crashplan from your Applications folder or from the menu bar at the top of your screen. Selecting "Show Crashplan" will launch the application.
When Crashplan opens, check the "Backup" tab, which will display the current backup status.