I tried too. Dunno how else you'd do it other than adding the gif addy like I did. Clearly this is over my head.
Animated gifs have been tricky so far. I'm assuming it has to be under a certain size. I haven't found that magic one yet.
When you went in to edit his avatar, there was a Yes or No option to resize it the user's maximum allowed dimensions. I just left it as Yes the first time, but switched to No and that worked.