Proper GIF Animation Upload to GrabCAD Website

I have a number of GIF files I'd like to upload and have them be the primary images when GrabCAD users visit my model library. I think I've optimized each animation to keep them as very small .gif files, but they don't appear or work in my library preview panel. I've only gotten 1 or 2 to work, while the others just show a blank generic cube. Can someone at GrabCAD give me insight into better .gif creation or formatting so that I post these better?
For an example, see the .gif animation associated with my 'pebble' shaped perfume bottle upload. (2nd image) associated with this upload.