Uploaded keynote file to iCloud through safari, after a day the iPad still could not see it when clicking the "+" sign at top left corner of Keynote in iPad.
Go to Settings in iOS device, click iCloud and turn it off for a while then turn it on again
People would ask why not using Google Drive to transfer the files. It is interesting that when you upload a keynote file to Google Drive, the file will become a set of files including data and various image files under a folder with the name of the keynote file, then it is useless to download it to the iOS, i.e. you cannot play anything about the original keynote file in your iOS devices.