First, make sure you have the correct battery and that the battery is charged.Make sure the battery is secure in the slot and the latch is fully closed. Next, try plugging your camera into a power source (i.e., computer, wall outlet). Plugging it in should prompt the device to power up.If you are not sure if your charger is working, you can try plugging your charger into another device to see if that device can be charged by the charger. For more information regarding power issues, visit the Troubleshooting Page for the Olympus Stylus 850SW.
If it seems like the battery is in the way, try removing the battery and inserting it again to make sure it is not blocking the latch from closing. If the latch to your battery enclosure is dysfunctional you may have a faulty spring. The spring within your camera is made of a highly malleable metal, making it easy to bend out of shape. Assure the end of the springs are not bent, as this will not allow the compartment to close fully. If the spring is defective and bent, you will need to replace it. For more information regarding a faulty battery latch, visit the Troubleshooting Page for the Olympus Stylus 850SW.