No picture taken when shutter release is pressed (by 2 users)

if you see no reation of the pressing of the button i.e. no focusing, no error message nothing , then most probably a simplest problem , the shutter release button may not be working for few reasons :
1) defective switch.
2) defective flex cable.
3) camera exposed to some physical jerk or dropping resulting into disalingment between inner switch and the shutter release button.