If you have troubles with Apple Numbers or Apple Pages or syncing with iCloud Drive you come to right place.

macOS Sonoma 14.0

Stop bird process via Activity Monitor or via killall bird in terminal. Check if works fine.

If you still have problems, then open Finder, press cmd + shift + G and type ~/Library/Application Support and return/enter. Rename folder CloudDocs to other name, for example CloudDocs-old. After renaming folder, stop bird process, this should create new fresh folder and syncing should start from scratch. It can take a while. If everything is OK, you can remove your CloudDocs-old folder.

Source: https://apple.stackexchange.com/questions/313716/icloud-drive-wont-sync-on-mac