I can't access my iCloud drive folders through Finder

Some days I cannot access folders and files in my iCloud drive through the Finder. The files are there, as I can access them through iCloud.com, BUT not through the finder. One of the most frustrating aspect of iCloud drive, namely it seems to be a bush-league cloud service, not worthy of Apple. Dropbox is not perfectly reliable either, but this is way worse! Any suggestion as to what to do (other than ditch the subscription and find a better cloud service)?

JP