How can I add candidate?

[coding-sunshine]

Hi How can I add candidate? When I try to add candidate passing the details it says me as follows:

(2/2) HttpException

Server error: `POST https://api.jobadder.com/v2/candidates` resulted in a `500 NullReferenceException` response:
{
"message": "Server Error"
}

Please see my code below

        $addCandidateCommand = new AddCandidateCommand();
        $addCandidateCommand->setFirstName($person->first_name);
        $addCandidateCommand->setLastName($person->last_name);
        $addCandidateCommand->setLastName($user->email);
        $addCandidateCommand->setLastName($person->mobile_number);
        $addCandidateCommand->setLastName($tickets);
        $response = $jobadder->candidates()->addCandidate($addCandidateCommand);