We are aware of the issue affecting tasks blocking you from completing week 1 of the Skate-o-Ween event.
We pushed a fix today allowing you to run any of the previously completed challenges again, "Witch's Brew", "Spider Bait", and "Heathen Flip", to complete the challenge goals and get all the week 1 rewards.
Additionally, we're disabling the "Basinator" Challenge due to the objective "Perform a single flip trick and 360 into the Fountain" not consistently tracking.