Some of the common problems and solutions are the following:
- iCloud documents not enabled. Check under: Settings > iCloud > Documents & data > set this to on
- iCloud for app not enabled. Check your app appears under: Settings > iCloud > storage & backup > manage storage
- iCloud is full
- Your firewall is blocking Internet access to apple servers
- You have no data saved
- iPad is a work iPad which is locked to prevent iCloud access. Speak to your IT department