Groups operating on the free, BASIC plan can only view the current month's board at any given time.
If your group formally competed using the Count.It PRO subscription, you can view the leaderboards of past challenges at any time.
Please note: Your challenge officially ends at 12AM - aka midnight in your group's timezone - on the last date listed. Count.It then allows 12 hours after the final challenge closes (aka - until 12PM the following day) for all users to sync their devices one last time to gather all remaining steps and for the leaderboards to recalculate. If you don't see the results posted to your PRO Admin--->Reporting page yet, wait to confirm your winners as your Leaderboard may still be showing the older rankings if calculations are still in progress...
To navigate back to a past challenge, select "Challenges" metric from the dropdown on your group homepage, and then click the left arrow to navigate backwards to all past challenges.