I noticed recently that some of my notebooks on my iPad Pro and iMac (which match just fine) are not syncing over to my iPhone correctly. For instance I had about 68 notes in a notebook called Madrid and they are all there in the iPad Pro and the iMac. However, on the iPhone, it is showing 0 notes in that notebook. I uninstalled Evernote, reinstalled , rebooted the phone. Same issue. Today I put a new note into my iMac in that folder and then checked the phone - the note was there, but none of the other 68 notes.
When I check the number of notes on my iMac it says I have 13,547 notes.