Originally Posted by
uanj
Did you try to change seats using the app? When you viewed your itininerary on the app did it show all flights? I don't know if the programmers behind the app know the rules on the website, but united.com is very clear that Silvers can choose Y+ seats when checking in if available.
From United.com: "Premier Silver members continue to enjoy complimentary space-available access to Economy Plus for themselves and one companion upon check-in."
If this was ticketed with ANA — which I suspect it was — the UA record would generally start with the previous flight before the UA-operated one. That might explain why the agent said OP needed to wait until 24 hours prior to the NRT-YVR flight, because that’d the first one on the UA PNR.