When I was tying to add test to cycle I am getting 500 error.

When I was tying to add test to cycle I am getting 500 error.
RequestSpecification addTestToTestCycle = RestAssured.given();
addTestToTestCycle.baseUri("baseURL");
JSONObject requestParams = new JSONObject();
requestParams.put("method", "1");
requestParams.put("issues", "ESM-33");
requestParams.put("versionId", "-1");
requestParams.put("cycleId", "30431");
requestParams.put("projectId", "15237");
requestParams.put("assigneeType", "");
addTestToTestCycle.header("Content-Type", "application/json");
addTestToTestCycle.header("Authorization", "Basic NSng4nNjn84njNDKNVK");
addTestToTestCycle.body(requestParams.toJSONString());
String addTestEndpoint = "/rest/zapi/latest/execution/addTestsToCycle";
System.out.println("addTestEndpoint : " + addTestEndpoint);
int status = addTestToTestCycle.post(addTestEndpoint).getStatusCode();
if (status == 200) {
    System.out.println("Test Added Successfully");
} else {
    System.out.println("Error while adding tests");
}
System.out.println(status);