I have tried accessing different videos on System Architect Essentials 8 but the audio isn't working on any.
Browsers : Chrome and IE tried so far.
Courses :How to navigate the Pega Platform ; Roles on a Pega project
Some learning assets, including "Roles on a Pega project" do not contain audio. I am not able to recreate the issues you are experiencing with the demos, including "How to navigate the Pega Platform". Does the demo video play, just without audio? Could you try un-enrolling and re-enrolling in the course?