The apples should be fresh. I usually will change them when they get dry/shriveled up. Make sure you set the hookholding up thedoor in a way that little pressure on the trip plate is needed to set the trap off.

Try wirering the apple down in the back of the trap. This will get the bunny pulling on the bait and adding more pressure to the trip plate. It also helps if you make a little trail of apple into the back of the trap. I usually put a small piece of apple a few inches outside the trap opening, one just inside the trap opening, one on the trip plate, and then a large piece in the back.

Good luck with both catchin a bunny and trainin your beagle!