Could not get response. (Internal Server Error)

when i try to get response

@Test
public void post01(){
    //set the url
    String url = "https://restful-booker.herokuapp.com/booking";

    //set the expected data
    BookingDatesPojo bookingDatesPojo=new BookingDatesPojo("2018-01-01","2019-01-01");
    BookingPojo expectedData = new BookingPojo("Jim","Brown",111,true,bookingDatesPojo, "Breakfast");
    System.out.println("expectedData = " + expectedData);

    //Send the request and get the response
    Response response = given().contentType(ContentType.JSON).body(expectedData).when().post(url);
    response.prettyPrint();

Why am I get "Internal Server Error" 

java version "11.0.15.1" 2022-04-22 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.15.1+2-LTS-10)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.15.1+2-LTS-10, mixed mode)