It's missing for everyone! The product has been updated with a new Design Center. The videos were recorded before the releases in July and November 2017. In order to successfully complete the course, you must create a NEW trial account, making sure to match the email you used to register in MuleSoft.U so that it will be automatically extended.
When you come across a video that does NOT match what's live in your new trial account, use the links at the bottom of each module to the Updated Slides and Updated Student Manual to get the latest training.