Scorpions prefer preys that move a lot, climb, jump, and especially fly. I can't say prefer, but they like it hard. Scorpions are used to it, leave it be. Like I did the other day, leave the prey in the tank. I left the beetle there, in the morning it ate it. It's hard to force sometimes, it's like hacking your favorite game and then you regret it after. This is somewhat their kind of behavior I've noticed.
I don't know if that's completely true though, but just leave the feeder in the tank. It'll devour it after. The beetle that it ate dug through the soil before. It was a large one.