If the balls are spawned on a player's bricks and that player is not in the server, you are unable to pick them up.
Try enabling "Use All Players' Bricks".
What do you mean?The vehicle?A tool?A body part?
walk onto the ball without your tools out, or even the inventory open
Who owns the bricks? Are they public?
Please try this using Freebuild or one of the other default game modes.