There are various reasons why the lens might have got stuck, perhaps the commonest being dust, dirt or sand getting in between the barrel sections. As it opens, the lens acts like a bellows and sucks air and any dust or dirt it might be carrying into the lens. Sometimes this can be cleared by slipping the corner of a piece of good quality paper between the barrel sections and running it round the barrel, checking the paper often for fraying, or applying a vacuum cleaner to suck out any dirt. I once succeeded (on another camera) by alternating those processes several times. Make sure the battery is fully charged to ensure the zoom motor is operating at full power. Gently pushing or pulling on the lens barrel (whichever way it seems to want to be going) as you turn the camera on may help.
Other causes, apart from physical damage (which may well be apparent from a misaligned barrel) could be malfunction of any of the several motors, positions sensors and gears within the lens and would be likely to involve full lens disassembly to diagnose and repair, which is a fairly skilled undertaking.