That is exactly what I use it for! That’s surely a legitimate use and 1st class on that route at the times I travel isn’t normally that busy.

I just looked at the route again when the occupancy is forecast to be 1/3 in both classes and the option still isn’t there. Also it doesn’t make sense if you look at DB’s post that you can upgrade for Zurich to beyond Pfäffikon on the same train.

So the not so detailed answer from SBB.

“Thank you for your query.

We are aware of this error and are endeavouring to find a solution. This will be integrated in a new version at a later date”

A timeline would have been helpful.

I think DB is right - it relates to ZVV somehow. I’ve just tested it and I can buy an upgrade to Altendorf, which is the first stop outside of the ZVV zones. I guess it can be used as an expensive workaround for now (CHF 7.70 vs CHF 4.90). Not the end of the world for a couple of times a month.

Try downloading the 'SBB Preview' app. to see if the fix has already been made there.
It is a test version of the 'SBB Mobile' app. where new features etc. are trialled.

Happy to report it’s working again. I don’t think there was an app upgrade. Good job as the train is quite busy this evening!