Same Happened to Me
I bought a full Y into EWR and the automatic upgrade never showed. The upgrade list didn't appear online (or in their mobile apps) so I'm not sure if I ever was on any upgrade/waitlist; when I checked-in, there was no remark on the boarding pass about standing by for the upgrade. Fortunately for UA, I misconnected and did not make the flight to EWR. When I was accommodated on the next flight (which was the following morning), I was booked into JN class in the forward cabin.