I put them in a cup of a tank water for a little bit
Maybe they haven't realized it's food yet.
I have had less luck with freeze dried, both blood worms and brine shrimp (except blood parrots, who would eat cheetos if I put it in there). Frozen foods seem to be more appetizing for them and also have the appearance of live food when they fall into the tank.
You could certainly try that, but soaking it first would be helpful as well as healthier. I find frozen blood worms to be a treat that no fish in my tanks can resist.