I also got this message a few days ago when an upgrade cleared, and I tried to ignore it for four days (over the weekend, just in case there's some kind of automated system that doesn't run on weekends). It was still there on Monday, so I called and the agent quickly refreshed the itinerary and it's no longer showing. While I understand it might be a system glitch and should ignore it, I found that during the time this message was showing, this particular itinerary didn't show up in my mobile app under "Reservations" at all. Once I called and got the message removed, the itinerary showed up again.