I see “Upload Failed” in PowerPoint when I try it and indeed I have a 0 byte file in iCloud Drive. I tried Word too and saw the same result as you though, it apparently saved without error but also left a 0 byte file. Wondered if it affected just Office or everything else so I tried Pixelmator and it saved to iCloud just fine.
Beta OS with an app that isn't upgraded to use said OS, yeah it could happen. Try opening the file from iCloud Drive on another device. See if its a bad save or just a bad size report
Beta OS with an app that isn't upgraded to use said OS, yeah it could happen. Try opening the file from iCloud Drive on another device. See if its a bad save or just a bad size report