The home for these videos has moved around a bit. The safest way to get there is to start with www.nxp.com/mqxv5 and select the 'Training & Support' tab at the top right. You should see the 'Essentials of MQX RTOS Application Development' link which will take you to a repository for online training. Type 'Essentials of MQX RTOS Application Development' into the search bar ( a shorter version of the title should work as well) and then select the MQX course when it comes up in the search. Somewhere along the way it may ask you to sign in to the NXP website with your login ID.