Mcreator testing server

The button to the right of the "Run Client" button is "Run Server And Client". A month ago i used this button just to see what it did and it was working fine. Now my server says "Old" in red next to the ping marker. When I try to join the server it says "Server is still starting! Please wait before reconnecting!" But no matter how long i wait, it says the same thing. Does anybody know how to fix this? I'm pretty desperate at this point!