On inter-carrier star alliance tickets (e.g. a US code-share on a UA flight) there is no certainty that the fare codes are the same on your ticket and on the reservation as seen by the operating carrier.

[EDIT] but have just realized that's irrelevant since this is on UA.com

I have had a similar problem with CO.com before - showing me in R without upgrading me. I think that one was fine in the end, IIRC EUA bumped me to F as normal and I would remember if I didn't get miles.