I will go update the "Due Date" of an issue in JIRA and then refresh the team calendar window. The issue does not appear. Note that I am toggling the due date of an issue that previously did not have a due date. However, if I create a new, identical calendar with that project's JIRA items, it will then show up. It's like it's not refreshing very often... and I haven't found a way to force a refresh outside of creating a new team calendar with the same content.