Canon EOS 90D Advanced User's Manual page 597

Shooting-Related Problems
The lens cannot be attached.
The camera cannot be used with RF or EF-M lenses ( = 54).

The viewfi nder is dark.
Install a recharged battery in the camera ( = 44).

No images can be shot or recorded.
Make sure the card is properly inserted ( = 48).

Slide the card's write-protect switch to the Write/Erase setting ( = 48).

If the card is full, replace the card or delete unnecessary images to make

space ( = 48, = 350).
You cannot take a picture when focusing with One-Shot AF and the focus

indicator < o > in the viewfi nder is blinking or when the AF point is orange
during Live View/movie shooting. Press the shutter button halfway again
to refocus automatically, or focus manually ( = 57, = 147).
Troubleshooting Guide
597