Canon EOS 80D Instruction Manual page 483

Shooting-Related Problems
The lens cannot be attached.
The camera cannot be used with EF-M lenses (p.47).
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The viewfinder is dark.
Install a recharged battery in the camera (p.34).
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No images can be shot or recorded.
Make sure if the card is properly inserted (p.37).
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Slide the card's write-protect switch to the write/erase position (p.37).
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If the card is full, replace the card or delete unnecessary images to
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make space (p.37, 378).
If you try to focus in the One-Shot AF mode and the focus indicator
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<o> in the viewfinder blinks, a picture cannot be taken. Press the
shutter button halfway again to refocus automatically, or focus
manually (p.50, 137).
The card cannot be used.
If a card error message is displayed, see page 39 or 496.
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I cannot lock the focus and recompose the shot.
Set the AF operation to One-Shot AF. Focus lock is not possible in the

AI Servo AF mode or when servo takes effect in AI Focus AF mode
(p.118).
Troubleshooting Guide
483