I'm getting error message when I try to upload an image to the course card, "There was an error uploading the image." I've done this before but it's not working now. I tried in Firefox and Chrome. Image is a 262 × 146 pixel .PNG. Tried on different courses -- no luck.
EDIT: Flicker import works ... 'drag drop' or 'browser my computer' doesn't.
**Limited success!! worked on my Mac; Yosemite; Safari only ... coworker got it to work on Mac, Sierra; on both Chrome and Safari.