iPhone Apple Notes not uploading to iCloud, only downloading from

Apple Notes on my iPhone 12 (iOS 16.4.1) is not uploading to iCloud, but it does download from iCloud.

If I create a folder or note on iCloud web, Mac, or iPad, the new item appears on my phone after a minute or two (as it should).

But if I create or modify something on my phone, the new/updated thing doesn't sync to iCloud or my other devices.

It used to work. I frequently would create notes on my phone and scan documents, later accessing those notes+scans on my computer. But recently, I found that the scan/attachment would be blank on my computer version of the note. And now, the phone note doesn't even appear on the computer (or iCloud).

This means there are notes and scans/attachments on my phone which are ONLY on my phone; thus, I am very reluctant to toggle the iCloud sync button on my phone, as I recall that can wipe all the notes from the phone.

This blank attachment problem began a few weeks ago, before my latest iOS update. So I don't believe this problem is related to the update. Also, my phone has been rebooted a few times. So the usual "reboot phone" advice is pointless, as is the "toggle notes icloud sync".

How can I force Apple Notes on my phone to push its new/updated data to iCloud?

Also, all my folders and notes are under the iCloud category of the app, so they are not being intentionally stored only on the phone.