Partipost or the brands managing the campaigns can take up to 10 days to review your submission - even after the step schedule has ended. Sit tight and wait for an email update or a push notification from us regarding the status of your submission. As long as you see your submission on the Partiposts tab, it's in the approval queue and you will be updated soon.
Since you cannot progress to the next step until your submission for the current step is approved, you might want to join a new campaign altogether while waiting.