I've been stuck on this issue for about 2 days, actively trying to solve it. SOLVED NOW! My iCloud Drive folders/files did not appear on my MacBook and newly created files were not uploaded to derive no matter what I did. I tried logging out/in, killing bird process, increasing priority of the process, digging down to the logs and so on... In the end, solution was pretty easy. BEFORE: I had 2 user accounts on my MacBook, work and private account. Work user account had work Apple ID as primary iCloud account and personal Apple ID as secondary iCloud account to only fetch events from private calendar. Private user account had personal Apple ID as a primary account. NOW: As soon as I removed personal Apple ID from work user account (used to be secondary account without possibility to sync files), syncing started to work on my private user account (personal Apple ID as primary iCloud account)! @apple - how about mentioning this somewhere in troubleshooting guides? Same Apple ID accounts cannot be used in 2 different user accounts on different level (primary vs. secondary) simultaneously?