Once no external flash is attached the built-in flash may not fire if the spring or metal switch in the hotshoe( the flash socket) that allows the flash to fire, is stuck. Dirt may be the cause of this. To fix it, clean the hotshoe with a soft brush or compressed air. If it still does not fire, unstick the spring with the help of a probe or pick. Slide the pick on the right side of the hotshoe to uplift the spring to its original position. See the troubleshooting page for more information. https://www.ifixit.com/Wiki/Canon_EOS_40D_Troubleshooting
+
Once no external flash is attached the built-in flash may not fire if the spring or metal switch in the hotshoe( the flash socket) that allows the flash to fire, is stuck. Dirt may be the cause of this. To fix it, clean the hotshoe with a soft brush or compressed air. If it still does not fire, unstick the spring with the help of a probe or pick. Slide the pick on the right side of the hotshoe to uplift the spring to its original position. See https://www.ifixit.com/Wiki/Canon_EOS_40D_Troubleshooting for more information.
Once no external flash is attached the built-in flash may not fire if the spring or metal switch in the hotshoe( the flash socket) that allows the flash to fire, is stuck. Dirt may be the cause of this. To fix it, clean the hotshoe with a soft brush or compressed air. If it still does not fire, unstick the spring with the help of a probe or pick. Slide the pick on the right side of the hotshoe to uplift the spring to its original position.
+
Once no external flash is attached the built-in flash may not fire if the spring or metal switch in the hotshoe( the flash socket) that allows the flash to fire, is stuck. Dirt may be the cause of this. To fix it, clean the hotshoe with a soft brush or compressed air. If it still does not fire, unstick the spring with the help of a probe or pick. Slide the pick on the right side of the hotshoe to uplift the spring to its original position. See the troubleshooting page for more information. https://www.ifixit.com/Wiki/Canon_EOS_40D_Troubleshooting
Once no external flash is attached the built-in flash may not fire if the spring in the hotshoe( the flash socket) is stuck. Dirt may be the cause of this. To fix it, clean the hotshoe with a soft brush or compressed air. If it still does not fire, unstick the spring with the help of a probe or pick. Slide the pick on the right side of the hotshoe to uplift the spring to its original position.
+
Once no external flash is attached the built-in flash may not fire if the spring or metal switch in the hotshoe( the flash socket) that allows the flash to fire, is stuck. Dirt may be the cause of this. To fix it, clean the hotshoe with a soft brush or compressed air. If it still does not fire, unstick the spring with the help of a probe or pick. Slide the pick on the right side of the hotshoe to uplift the spring to its original position.
Once no external flash is attached the built-in flash may not fire if the spring in the hotshoe( the flash socket) is stuck. Dirt may be the cause of this. To fix it, clean the hotshoe with a soft brush or compressed air. If it still does not fire, unstick the spring with the help of a probe or pick. Slide the pick on the right side of the hotshoe to uplift the spring to its original position.