If you set-up the game and the lower tension rope seems too short, because it does not reach the lower eye bolts (used to tighten and tension the net), please check you have connected Pole B the right way up.
The eye-bolts on Pole B are located nearer the top end.
If the eye-bolts are nearer the bottom-end of Pole B, it is upside down, so please disconnect and reconnect the right way up.