I'm unable to close a sprint on a team-managed board due to open subtasks included in the sprint; however, the flagged parent work items and all their subtasks are all in "done" statuses (most "done," some "won't do).
I've done a filter search for any unresolved work items, including subtasks, in the sprint. I've logged out of jira and back in again, in case it's a caching issue.
One other thing to note, did start the next sprint when I couldn't get unblocked on closing the old sprint, which I understand might have me in even more of a bind when it comes to closing the old sprint, but here we are.