As the message says. your URL is invalid. Instead of
http://localhost:8080, you typed
http://localhost/8080 .
But something's listening on port 80, and if it's not nginx, it might be IIS or it might be some other app. In Linux, I could easily tell what that program was using
netstat, but I'm not sure if the Windows version of
netstat does that.
I'd be tempted to say it's the Spring Boot app itself, except that that's not a
Tomcat 404 page, which is what I'd expect Spring Boot to serve. Plus to listen on port 80, you have to have administrator privileges.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.