There may be several reasons why your device may not be powering on. Following are the common ones:
* The battery may not be sufficiently charged. It may discharge automatically if not used over a long period of time. In this case, simply charge the battery. Also, check to make that the battery is inserted in correct orientation.
* The battery terminal may not be clean. You may clean the terminal with microfiber.
* External temperature also effects the way the camera functions. Thus, make sure to not use the camera when the temperature is above or below 0-40° C. Condensation might occur if the camera is moved from extremely cold temperature to a warm environment, which could prevent the camera from functioning properly. In that case, let it come to room temperature and allow the condensation to evaporate naturally.
* For more information, refer to the [[Sony Cyber-shot DSC-W800 Troubleshooting|troubleshooting page]].