I created an epic, a story with sub-tasks, and a story without sub-tasks. I assigned both of the stories to the epic. When I click on the Backlog page, I see the epic labels next to both stories, as expected.
When I click on the Active Sprints page, I only see the epic labels next to the story with no sub-tasks. The story with the sub-tasks doesn't have the epic link, and neither do any of the sub-tasks.
Is this default JIRA behavior, or am I just missing something basic?