Your problem may be that you are running the server on your machine. If so, you need to change your Authserverip to localhost.
However, I recommend joining Jonny’s server (The link is at the bottom of the page). Then, change your Authserverip to lu.jonnyvps.de, and login using the username/password you signed up in.
Remember, before you ask questions, search it up in the FAQ or use the search bar.
Also, if your native language is Spanish or German, you can click those links in the Preferred Language box, and it will translate this page.