Have been getting this problem for sometime around. (4 times in past few months)
I'm logged into my account, the internet connection is on. My device time is in sync with servers.
However on day of beginning of a new tournament, when I log into the game and scroll on to WTTT tab, it shows a new tournament has started, without allowing me to claim the reward from previous tournament. It's quite unfair to be honest.
Got in touch with support, response was "there are no bugs. WTTT is working as intended"