From SenseCam Wiki
Common Support Questions
Q. My Revue camera isn't working as expected
A. Switch the device off and on again, and then reconnect to the computer. If nothing happens carry out a ‘hard reset’. Simultaneously press and hold down for five seconds the privacy button (the top side button) and the on-off button, as shown in the image. Use the device for a short time and test to see if it’s now working.
Q. There are no lights on my Revue camera
A. The device may have gone into 'deep sleep' mode because the battery is too low. To get it going carry out a hard reset as stated above and charge for a minimum of 6 hours. When the device IS in deep sleep, it is still possible to charge it as usual although there will be no lights indicating that it is charging.