just to confirm. Is the code in codepen being copied into the fCC page exactly as-is?
(so for eg. I can copy the codepen html into the index.html without any changes? if you are making any changes, then we need to see the actual code you are using in fCC side, so post that in full here)
okay, it wouldn’t be a link. (it would be a cut and paste)
But anyway, I tried your code and the only issue I saw is that you didn’t actually link the stylesheet