The 5x Rank EXP in Multiplayer Ultimate Arena-No Continues bonus began as scheduled on Monday, 9/3, at 12:00 AM (UTC-8). While the bonus is in effect either way, the in-game message announcing the bonus may not be displaying for all players. If you are affected, returning to the title screen or rebooting the app will cause the message to be displayed.
As always, thank you for playing Puzzle & Dragons.