gimp, gifmaker.me and ezgif for dont work
and it's still giving you that error? hmm. do you know where the gif came from?
and how big is the file? if it's less than 5MB you could try uploading it to imgur, then saving it, and try using it as your avatar again. idk if that'll work, or not, but it's probably worth a shot, since it's not hard to do