Post#15: I had a lot of trouble when I 1st got mine. The cap mechanism engages and draws up as you turn it into place. Somehow on the 1st fillup I got mine in the drawn up position before trying to turn it -- so it wouldnt turn. What i had to do is engage the slots and turn it 1/4turn ccw to return it to "ready". Then place the cap in with the fold out butterfly handle oriented vertical, hold in gently and turn it til the handle was horizontal. This engaged the dogs and drew the O-ring seal into place. Success.:thumbsup:
larry