Are you sure the battery still has enough power (even after charging) to let the lens motor do its job?
Are you sure there is no mechanical problem, you can see on the outside? Did anyone stop the lens, while it was coming out? Did anyone drop the camera, while the lens was out?
There cam be a lot of reasons, why a lens won't retract. Could be some force was used, also could be something just went wrong inside the camera. Like a gear that broke inside, or the motor stopped working. A contact failed and perhaps lots of other things.
If you already took out the battery, and reinserted it, and nothing changed, The only thing you than can do is after getting the battery out, is recharge the battery and then put it in.
If you have a spare battery, or you know anyone who has the same battery, try that battery. If nothing indicates a mechanical failure, and nothing helps, just contact the Canon Service Centre closest to you. First ask what a possible repair will cost. hen decide if you would like it repaired or you want a new camera.
New camera's are much better and cheaper than cameras last year.
on Feb 15, 2014