Hello slow_and_simple,
Thanks for reaching out to the Apple Support Community. I understand you have had some trouble with some missing documents in iCloud, and I have some information that may help.
Have a look at the excerpt from the article below for some helpful troubleshooting steps. You may have completed some of the later steps, but some of the others may help determine if your files are still accessible but not syncing to your device.
Get help with iCloud Drive - Apple Support
When you turn on iCloud Drive, any documents that you already store in iCloud automatically move to iCloud Drive. You can see your files on iCloud.com in the iCloud Drive app and iWork apps (Pages, Numbers, and Keynote).
If you don’t see your files in the iWork apps or in iCloud Drive, make sure that you set up iCloud Drive on all of your devices. If you don't see the files from your Mac Desktop and Documents folder on iCloud.com, go to System Preferences > iCloud, then click Options next to iCloud Drive and make sure that it's turned on.
If you need to access a file that you deleted within the last 30 days, you can recover it.
- Sign in to iCloud.com.
- Click Settings.
- Under Advanced, click Restore Files.
- Browse the list of files in the Restore Files window.
Files are removed from Restore Files in 30 days.
If you run into any trouble, please reach out again.
Best Regards.