Erro metodo HTTP POST na hora de testar no POSTMAN

Segue passo a passo da vídeo aula e deu erro, baixei o código pronto e continua dando erro no POSTMAN

Could not get any response There was an error connecting to . Why this might have happened: The server couldn't send a response: Ensure that the backend is working properly Self-signed SSL certificates are being blocked: Fix this by turning off 'SSL certificate verification' in Settings > General Proxy configured incorrectly Ensure that proxy is configured correctly in Settings > Proxy Request timeout:

Change request timeout in Settings > General

package br.com.alura.forum.controller;

import java.net.URI; import java.util.List;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.util.UriComponentsBuilder;

import br.com.alura.forum.controller.dto.TopicoDto; import br.com.alura.forum.controller.form.TopicoForm; import br.com.alura.forum.modelo.Topico; import br.com.alura.forum.repository.CursoRepository; import br.com.alura.forum.repository.TopicoRepository;

@RestController @RequestMapping("/topicos") public class TopicosController {

@Autowired
private TopicoRepository topicoRepository;

@Autowired
private CursoRepository cursoRepository;

@GetMapping
public List<TopicoDto> lista(String nomeCurso) {
    if (nomeCurso == null) {
        List<Topico> topicos = topicoRepository.findAll();
        return TopicoDto.converter(topicos);
    } else {
        List<Topico> topicos = topicoRepository.findByCursoNome(nomeCurso);
        return TopicoDto.converter(topicos);
    }
}

@PostMapping
public ResponseEntity<TopicoDto> cadastrar(@RequestBody @Valid TopicoForm form, UriComponentsBuilder uriBuilder) {
    Topico topico = form.converter(cursoRepository);
    topicoRepository.save(topico);

    URI uri = uriBuilder.path("/topicos/{id}").buildAndExpand(topico.getId()).toUri();
    return ResponseEntity.created(uri).body(new TopicoDto(topico));
}

}