Hey bbumblebeenis ,
This error indicates that the video player cannot play this type of file.
Can you tell me which file you are trying to view on a video player?
I am guessing it is the video file included in the source files.
If so, this is the 10 second video of the tutors version of the rocket launch.
It is the same as you see at the beginning of the course.
Although this is an mp4 file, I believe this is an older version, no longer supported in media players as standard.