Docker is not installed. Please install Docker, then try again.
Make sure Docker is open and running, then try again.
This means the default port is already in use. In your .env file just specify a different port:
PROXY_PORT=3030
And now try again.
If you see one of these error messages in your browser after you started WordPressify, means that files are still being prepared. Just give it a few more moments and reload the page.