There are several possibilities:

If your battery was low when you turned off the camera, it is possible the lens did not retract all the way.
You can lay the camera on its back and gently press on the front of the lens to help it retract.
Avoid touching the center of the lens or lens cover.
Then test.
But this time watch the LCD screen when you power-on the camera.
See if a message is being displayed on the LCD screen.

If the camera was dropped with the lens extended, the lens could be knocked out of alignment.
You may (or may not) be able to fix it.
Lay the camera on its back and look closely at the rings that surround the lens.
The rings are the telescoped sections of the lens.
See if they are equal distance apart on all sides.
If not, gently press on the sides of the rings that are further apart and see if they will snap back into alignment.

If the lens tries to extend when you power-on the camera, try to assist the lens by gently pulling on the lens housing.

Good Luck