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A code 20 means, roughly, that the mechanism of the camera has a problem.
Try a different lens assembly on the camera, after turning it Off again of course.
Then try cleaning the terminals in the battery compartment, after removing the batteries, first by rubbing off with a fresh pencil eraser, then by wiping the terminals off with cotton swabs moistened in rubbing alcohol, then letting them dry off for 5+ minutes with the battery compartment door open, then try turning the camera On again.
Has the camera been dropped or otherwise subjected to mechanical shock(s) in its lifetime?
Has the camera been operated in or subjected to, temperatures below 32 degrees F (freezing point) or above about 100 degrees F ?
Has it ever been subjected to a humidity higher than 85 % or gotten wet ?
Has the camera been operated in a gritty or sandy environment, such as a beach, a seaside, a construction site, or the like?
Good to hear that!
That is quite promising, actually, so I will mark this as an answer.
But be warned: if this error happens again, call 1-800-OK-CANON, before your camera becomes 12 months old on the dot and its warranty coverage expires, and put in a failed-within-warranty claim on it for free-of-charge repair by Canon (whose repair department is generally praised for rapidity of turnaround time and good quality).