I made a video at home, and when I got on it at school to show it did not work and I was sent back onto the first slide. I fear it was deleted on my other account too.
Can you see the video you created in your files? Did you make the video from a template or not?
If you've created the video while logging in to an account, it's not automatically transferred to another account. The projects are automatically saved while you're working on them. Did you try to download your video while you finished it?
Did you try to play the video from another browser?
Can you share your video so we can understand the problem?