I can't connect to the server.

While working on a project, suddenly, while checking the function of connecting to the server, the connection does not want to work. Well, the way it works is that a server is created, but when I search for a server and connect to it, it doesn’t work. First of all, the information about logged in users shows me that there are 0 logged in users, whereas previously it showed me 1 after creating the server, because of course it is a server, but when I load the searched server it shows 0 logged in users. But there I think “Oh there.”, but when I log in, instead of being transferred to the server, I am on a screen with options. I look at the title screen to see if Play as server is working. Works. Where to open it. Works. But it won’t move the client during the real test. What should I do?