Sometimes iCloud Drive seems to be stuck. The symbol in the sidebar in the Finder doesn't complete, and usually stops almost at the end (almost completed circle).
There is a background process called "bird" which handles this function. Try restarting it from Terminal, using:
killall bird
This will shutdown the process, and the OS should restart it automatically. Give it a few minutes and see if the sync completes.
If that doesn't work, try restarting the computer. Again, wait a few minutes after the restart to see if the sync process completes.
If that also fails, try looking through the files and find those with the not synced (there is an incomplete cloud syn icon next to them). Move them out of the iCloud location and see if the sync completes. Move them back if it does, and hope the sync then copies those as well. If not, try opening and re-saving them.
If all else fails, you can erase the local copy of files and have it re-built. I strongly recommend making a backup first (use Time Machine so all files are copied, or copy the CloudDocs folder in Application Support in the user Library).
Warning: Don't do this if you are unsure about backups, etc.
Here's how to erase the current cloud files and force a complete re-sync:
Open Terminal and type these 2 lines: cd ~/Library/Application\ Support rm -rf CloudDocs
All the files then re-sync from the cloud. Note this could take hours or even days.
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