I would like for the opponent ai to chase the tennis ball

Hello. Im trying to make a tennis game and I’m kind of stuck.
I would like for the opponent to chase the ball afters it’s been spawned from the player.
I keep trying to use the tennis ball blueprint as an object reference variable but it keeps giving me errors and doesn’t recognize it. So far I have it so the ball is spawned and it has momentum but that’s about it for now.