why does the immersive video not play on Apple Vision Pro

I have the exact same issue.

rebooting the vision pro solved the issue.

Sign out of your apple account and resign in or simply clear your history. This will work for now! Apple support is completely incompetent as you may have noticed.

I am experiencing the same issue more frequently, not only with immersive video now.

I have signed out/signed in, and it worked for a while, then back to the same issue.

It's the same for rebooting.

This also happened to me when I had my Apple Vision Pro being cast to my laptop. It started working when I turned off the casting.