Photo Stream won't accept my EOS 6D JPEGs

Hi all. I just purchased a Canon EOS 6D. Aperture is set to automatically upload new photos to My Photo Stream. I've imported two events into Aperture. None of them uploaded automatically (while photos taken with my iPhone upload fine). I tried manually putting them into My Photo Stream but that didn't work. I tried dragging and dropping the photos into the photo stream and also using the share button. The animation makes it look like the photos are zooming over to the Photo Stream but that never happens.

I tried making a new photostream out of one of my events and that worked just fine. It automatically downsampled the JPEGs and created a new photostream/uploaded the pics. I'm out of ideas. Do you have any?

Photos are 20 megapixel JPEGs. Running the latest version of Aperture on the latest version of Mountain Lion.