Canon MARK IV User Manual (en)

Troubleshooting Guide
Auto power off is in effect. If you do not want auto power off to take 
effect, set [5 Auto power off] to [Off].
The camera cannot be used with EF-S lenses (p.39).
If a card error message is displayed, see page 38 or 256.
The card is not properly inserted (p.36).
If you are using an SD card, set the write-protect switch upward (p.36).
If the card is full, replace the card or delete unnecessary images to 
make room (p.36, 179).
If you try to focus in One-Shot AF mode while the focus confirmation 
light <o> in the viewfinder blinks, a picture cannot be taken. Press the 
shutter button halfway again to focus, or focus manually (p.41, 95, 
Set the lens focus mode switch to <AF> (p.39).
To prevent camera shake, hold the camera still and press the shutter 
button gently (p.40, 41).
If the lens has an Image Stabilizer, set the IS switch to <1>.
The camera turns off by itself.
Shooting-Related Problems
The lens cannot be attached.
The card cannot be used.
No images can be shot or recorded.
The image is out of focus.