Yes, it might be because you have made the filename all uppercase.

If you have a free account, it might be possible that the .ico extension is not allowed and the file didn't upload properly.

Try making the link and the file lowercase.

(p.s. you wrote the same question twice, by accident I think, probably by doubleclicking the button accidently. I deleted the other message because it was identical and so that people only answer to this one)