First step in growing Tropical Canna’s from a seed involves chipping the seed. Canna seeds have a very hard coating which wears down over time in a moist environment. If you simply planted the seeds, whole, germination will be more unpredictable. By chipping the seed you are in control of timings.
A certain amount of pressure needs to be applied to scratch the seed coating. Don’t go too deep, just until you can see the white inside.
This may take a little practice. The seeds have a tendency to slip off fingers and all over the place.