There’s a detailed discussion of the same issue here https://www.reddit.com/r/webdev/comments/1rj1oac/i_planted_f...
Indeed, it looks like CodePen v1 was sending data to codepen.io, cpwebassets.codepen.io, and cdpn.io. Now v2 sends to codepen.dev
Indeed, it looks like CodePen v1 was sending data to codepen.io, cpwebassets.codepen.io, and cdpn.io. Now v2 sends to codepen.dev