If you are expecting to see Shifts, Roles, or Volunteers when looking at the different Schedule views but are not seeing anything, it means that either you have not started to build out the schedule or that all the Shifts within the Opportunity are in the past.
When navigating to the Shifts page, the default view is to show Today & Upcoming Six Months shifts, roles, and scheduled volunteers. The Scheduled views will appear blank if you do not have anything scheduled in this date range. You will need to select a different option on the date-range dropdown to see any of the past shifts, roles, or scheduled volunteers.