One way to extend the end date of a scheduled report is to click the warning that is on the dashboard. Clicking that warning message it will take us to the Scheduled Items page. There we can update the report's schedule with a new Valid From date range.

We can also change the Valid From date range by following these steps:
  1. Click Home
  2. Next to Scheduled Items, click See All
  3. Select the report listed on the left side of the screen (if you don't see it, try setting the Show Items For drop down menu at the top to My Organization)
  4. In the Valid From Date, set the start date today and the end date to 1 year from today
  5. Also ensure that the box next to Disabled is unchecked
  6. Click Update