1. The memory card is full. Insert another memory card or delete some images from the current memory card.
2. With the camera in AF-S focus mode and the focus priority set to Focus, the shutter will not release if the subject is not in focus.
3. The camera shutter-release can be locked when Release locked is selected for Slot empty release lock in the setup menu and no memory card is inserted.
4. Shutter-release is not possible when mode S is selected with Bulb or Time chosen for shutter speed.
5. When using a CPU lens with an aperture ring (such as 'D type lens'), if the aperture ring is not locked on the minimum aperture setting then 'FEE' will be displayed in the control panel. Once set to the minimum aperture and locked, the shutter can then be released.
6. For cameras with a touch-screen, check that the touch-screen is not disabled in the camera setup menu.
7. If the battery is exhausted while images remain in the buffer, the shutter release will be disabled and the images transferred to the memory card.
