Upcoming reservation DEN-SNA-DEN showed 'upgrade to united first for $58 or 15000 miles' in View Reservations on united.com. When clicking on the offer, the dollar upfare is unavailable - I tried several times. Web support was able to replicate the situation but claims this is all well and good because the mileage upgrade part of the offer happens to be available. Isn't UA on the hook to honor the dollar upgrade? If so, how does one compel UA to do so?
(Closest thread I could find - if incorrect, please move post.)