What are you using to play it again? I suppose you're using DOPlay, but that won't work because the tween has already played, so you'll need to use DORestart instead.
Also, I have a suggestion, considering that you practically have the same tween, just going in different directions. Instead of having two tweens, you could have only one. Then, when you want to play it "forward", you call DOPlayForward, and when you want to play it backwards you call DOPlayBackwards