I had this issue and resolved it for myself, wanted to document it here in case anyone else runs into this.
The .ssh folder was missing on the instance compared to the video.
Turns out I had enabled OS Login when playing around the project earlier, see how to enable/disable this here: https://cloud.google.com/compute/docs/instances/managing-instance-access#enable_oslogin
That’s a really interesting find and makes a lot of sense if it’s replacing how the SSH keys work for the instances in GCE. In my experience, sometimes the best ways to learn come from tinkering and breaking things (then figuring out how and why!)
Hope this helps some other students, thanks for sharing!