Have you already found a solution? If not, I've replied my solution to OP. Maybe it'll fix it for your issue too.

Did you by any chance make a copy of a previous activity?I copied a couple of older/previous activities and made some changes and couldn't QA the test. Turned out on the Goals & Settings page the duration end date was still set to a date in the past. When I changed it to "when deactivated" the QA li...