Pool Party mission not appearing on the League client.

Hello!

I've been having an issue with my League client today. A few hours ago, I completed the fourth "Fun in the Not-Sun" mission, where you have to win 4 games or wear a Snowdown skin in a game. However, when I checked the missions tab soon after, I couldn't find the fifth mission in the series. I played some more games, but it refused to show up.

Should I wait a bit for it to appear, submit a form on the Report a Bug page, or should i send in a ticket to Riot Support?

Thank you for your time.