I've found Notes to be the flakiest. When I migrated my cloud service usage over to iCloud, it was the one part that caused me the most headaches. While most of the others "just worked" as advertised, Notes syncing took a long time to get going. Give it a while and disable/re-enable it later. I know that sounds like a simple answer but you'd be surprised.
Ouch, no wonder I don't use or trust iCloud much. I just did a web search on Notes don't show up on Macbook, and as vansmith says - and flaky seems to be a bit of an understatement going by all the hits.
One that just might help was some suggestions at: iCloud won
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