Do you happen to remember how you booked your ticket originally, and what fare class?
Last summer, I tried to update a ticket to PE, then PE to J. The J upgrade never stuck despite being charged (twice, for two attempts!)
A few days ago, I had a booking in economy (V fare) for two, paid $760 for the upgrade and then today the upgrade disappeared from the app and online site.
I want to like Swiss, but damn this is frustrating.