Kickstart iCloud Drive sync on your Mac
With regard to MGG870, I too have experienced flakiness in iCloud Drive's syncing, in my case with my iMac not syncing properly. Here's what happened and how I created a workaround. I need to download files from the web on my iPhone occasionally, which then get processed on my iMac with Hazel. But I was finding that the file wasn't showing up on the iMac because sync wasn't happening. I learned that if I created an empty folder in iCloud Drive on the Mac, it kickstarted the syncing process. So, I created a Keyboard Maestro macro that runs every 90 minutes to kick iCloud in the pants by doing just that. So far it's worked.