Well first try and determine if it is a mechanical problem, electrical or the firmware/software within it.
Does it even try to retract and stalls..error code ?
Go to your menu and do a "reset all " see if that helps.
You can also try rmoving the battery and holding the power button on for 60 seconds the try it again
Download and reinstall your firware from the Canon website
Hopefully one of those will help you before you need to send it in for service
