For Mac users, when you experience problems with the Finder like not being able to directly access your Asustor after booting up your client computer or not being able to see the Asustor NAS at all.
Also when you experience things like copying large folder structures taking up a long time.
This is applicable for 10.14 Mojave and possibly other MacOS versions.
Go to (username) ~/Library/Caches/CloudKit
Delete the CloudKitMetadata, CloudKitMetadata-shm, CloudKitMetadata-wal
Run Activity Monitor and kill/stop the process cloudd
Reboot
These caches will be rebuild automatically and cloudd will also restart
Remember to backup your files by all means (although this procedure is rather safe).