Why didnt my mission complete?

I have only a few hours left to finish the pool party mission "Fun in the Sun 6/6" It updated my progress normally when won my first ARAM game. But when I won my second game, it still remains at 1 out of 2 games. Why is that? If you look at my gaming history, you'll find that I have finished, and won 2 ARAM games. I lost a thrid one because I tried to win another to see if it would update. But I need to go to work soon and don't have time to play another. By the time I return, the mission will have long expired. Please help