After messing around with this a little more... Per the attachment, status bar looks as if the notebook is still trying to download. However, spot checking notes new and old for offline availability, it appears sync is complete. Evernote on laptop (MacOS) and app on iPhone agree there are 2032 notes, and edits on one propagate to the other. Changes get pushed to the phone, but sometimes the computer app needs to be reminded to pick up the changes.
Viewing my main notebook on the phone, I clicked on the three dots at upper right of screen. And was surprised to see the "Available offline" option not selected. I selected it, after which it greyed out. This was odd, because I had already launched the offline option from the Settings menu, and the notes had already downloaded.
So maybe there is a user interface issue.