Snippet dont work function AutoEmail

Why dont work?
https://prnt.sc/Bx10PPcpLn6y

$(document).on( "input", "#user_login", function AutoEmail() {
        var x= $('#user_login').val();
      if( x != "" ) {
          $('#user_email').val(x+'@test.com');
      } else {
         $('#user_email').val("");
      }
       
    });