Keynote file format may not be supported in some cases.
Ctrl + click the file and if you see "Show Package Contents" in the menu, you can't upload this file since this is a folder.

Should you wish to upload, please try the followings :

- Compress the file with .zip
- For Keynote version 6 and above, click File > Export > Keynote '09
- For Keynote version 5 and under, click Keynote Preferences > General > Uncheck "Save new documents as packages"