We tend to find that a fresh launch tends to fix things so try the following:

1) Close all the apps running on your device, starting with the game
2) Check to make sure you have ample storage on your device (and clear your device's cache too)
3) Turn your device off and on (restart tends to do the trick)
4) Then launch the game before you launch anything else
5) Check that back up for the Dan The Man app has been enabled in your Google Play Games or iCloud account. These cloud save options are used to store player data.

Note: If you played while your device was offline or in airplane mode, your progress may not be synced to the cloud. If this happens, your game will revert to the last successful save before going offline.