"Available Offline" Working?

I would like to have a copy of a document available on my phone even with no network access, i.e. a copy is on the phone. I am guessing (absent a manual) that the way to do that is to find the file in the IOS client, hit the three dot icon to the right of the file name, and “Set as available offline”. However, this does not appear to work.

I see a little green checkmark icon, or a little green down arrow icon, next to files I’ve tried making available offline, but file access absent a network still fails.

It appears I have “Nextcloud Coherence for iOS © 2021”.