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The planner shows a third dimension, different from the dimension(s) previously chosen in the backlog area. This means that you cannot select the same dimension as in the backlog e.g., if we have selected a board with priority by sprint, we won't be able to select the sprints dimension in the planner.
If you miss any of the three dimensions - sprints, releases or components - make sure that you have those selected in "Manage fields", within the Canvas administration.
Planning your Sprints
sprint planning
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