The most common cause is weak batteries.

If your rechargeable batteries that are over 4 years old, I would suspect you have one defective battery.
That is a common failure.
But you can't just replace that one battery.
You must replace the whole set of batteries.

As I test, I would install new AA Alkaline batteries and see if that helps.

If it is not a battery problem, try manually assisting the lens.
Gently push on the front lens housing when it tries to retract.
Gently!

Next, try gently pulling on the lens housing just in case the lens never fully extended in the first place.
Gently!

If that does not work, time to call Canon Service

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