Thanks, ! You beat me to it! 
Also take a look at this project: https://forums.unrealengine/showthread.php?52865-Sample-Project-to-destroy-Destructible-Mesh-with-Line-Trace-and-Ball-projectile
I set this up a while back for another user for test purposes and made it public to help out. The tutorial linked above that is a rough draft I did should help out as well. The projectile stuff is covered starting with Step 10.
Essentially what all this will cover is setting up the collision channels so that the YB Projectile and the Destructible know how to interact with each other. This is not something that is set up automatically which can lead to the frustration you’ve run into. I started out the same way banging my head against a wall until I got used to the editor and how things all work together.
If you have any questions feel free to post and I’ll gladly help out.