Has the ADF paper chute (cover)/feed guide been opened causing the ScanSnap to stay on even though the ScanSnap has not been used for a certain period of time?
If the ScanSnap is compliant with "ErP Lot6", a regulation for energy saving, the ScanSnap will turn off automatically when it is left unused with the power on for the specified time (default is [After 20 minutes]) after it is turned on by opening the ADF paper chute (cover).