Advantage of the sticky pads is a clean look and no holes in the car to rust or let in water. Less of an issue on a plastic bumper.
In my experience the sticky pads need to be warm, as does the car and plate, then they stick well. If any is cold, they can let go within weeks. Warm day? Or hairdryer. Hot air gun works, but mind you don't melt or set fire to anything, especially the car.
Hairdryer or hot air gun may be useful to get them off again, just a theory.