Hey there-- looking over the linked blog post, and the error message you’ve gotten, it doesn’t look like flyctl is able to locate your Dockerfile (since it would try to use your Dockerfile by default if knew where the Dockerfile is located) .
I would make sure that you’re running fly deploy -a app, (so that you know you’re deploying it to the right app) and making sure that you’re running fly deploy in your project root so that it knows where to look.
If that still fails, try seeing what happens when you manually specify your Dockerfile with --dockerfile.