I had a paid RT Polaris DEN-HKG-BKK and return (return on 12/24) booked over a month ago. The seat map was basically empty, and I made my choice. I woke up to a Call United message, and looking at the app, all three return segments are now listed as "waitlisted." Why would I now be waitlisted on all three flights where I had confirmed reservations? Before I call, I'd appreciate any thoughts as to what might be going on. The outbound flights are intact.