What error are you getting if you do try to connect them? Also, placing orphaned nodes is not a good idea, drag a data / exec wire first and then search - this will avoid a lot of mistakes.
Try dragging from the blue pin and search for “Launch”
Tried it. Its not working
You are spawning BP projectilemain but the launch event looks to be from the BP projectile do you this same function in BP projectilemain?