Folders missing in sync iPhone
I keep my pictures in separate folders - in my case, in a larger Pictures folder under my user name (and not in Photos / iCloud Photos) on my Mac.
If you open my iPhone for syncing (Finder > my Phone), and click thru the Photos tab, you'll see I have set up 'Sync photos to your device from: Pictures (the route to the main folder), and chosen 'Select folders' - with some sub-folders chosen.
Syncing seems to go off okay, but in reviewing the folders on the iPhone, some of the chosen folders simply aren't there. I have trying unchecking the missing folders in 'Select folders' and re-syncing, then re-enabling them and syncing. Nope. I have fully uninstalled all photos from my iPhone and the sync option and then re-syncing. Nope.
This shouldn't be an iCloud Photos issue because I'm asking the sync to choose a local folder on my computer. Perplexed as to why its only some folders - no rhyme or reason, as far as I can tell.
While I am currently on Monterey, this has been an issue for a couple of OSs now.
iPhone 12 mini, iOS 16