Canon EOS-1D X Instruction Manual page 393

Operation Problems
I cannot change the setting with <6>, <5>, or <9>.
Set the power switch to <1> (p.38).
Check the [85: Multi function lock] setting (p.337).
Vertical-grip controls such as <6> and <9> do not work.
Set the vertical-grip operation switch to <1> (p.49).
The camera button/dial's function has changed.
Check the [85: Custom Controls] setting (p.343).
Display Problems
The file name's first character is an underscore ("_").
Set the color space to sRGB. If Adobe RGB is set, the first character
will be an underscore (p.168).
The fourth character in the file name changes.
With [51: File name], select the camera's unique file name or the file
name registered under User setting 1 (p.162).
Troubleshooting Guide
393