Thank you for the answer, but unfortunately my problem isn’t none of these.
I have some folders locally on my PC, inside C:\Users\Jorge\iCloudDrive. They should sync automatically (and they did), but a few weeks ago they stop synchronizing. The files's status is “Sync pending”.
If I click the iCloud icon (on the status bar) I can see “Sending xxx elements”, but that xxx number never changes, so it appears that sync has stopped. I can’t find any “force sync”, or “stop sync/pause sync” option anywhere, as OneDrive and Dropbox have.
If I create a new file, the xxx increments by one. If I delete that same file, the xxx doesn’t decrement.
I've already left the PC connectd a hole day, just to see if it finishes synching (or xxx decrements).
It does appear that the sync process is stuck in some file.
I have already rebooted the PC, tried another network connection (wired and wireless).