There should be a spring that pushes the card out, and a catch that latches it in place when you insert the card.
When you push the card down to eject it, the catch releases and the spring pushes the card up.
Sounds like the SD slot eject mechanism is broken - if it was refurbished then Canon would have fixed this.
Whatever has been broken is possibly also interfering with the card-lock microswitch.
Phil.