How to track down an error when sending ajax or why the request is not sent?

Question

JavaScript

$('.reg-button').on('click',function(){
  var data = {
    name: $('#reg-login').val(),
    email: $('#reg-email').val(),
    password: $('#reg-password').val(),
    repassword: $('#reg-re-password').val()
    },
    validmail = /^[a-z0-9_-][email protected][a-z0-9-]+\.([a-z]{1,6}\.)?[a-z]{2,6}$/i;
  if($.trim(data.name) == '' || $.trim(data.email) == '' || $.trim(data.password) == '' || $.trim(data.repassword) == ''){
    $('.message-register').text('Одно или несколько полей не заполнены');
  }else if(data.password != data.repassword){
    $('.message-register').text('Пароли не совпадают');
  }else if(data.email.search(validmail) == -1){
    $('.message-register').text('Проверьте правильность почты');
  }else{
    $.ajax({
      type: 'POST',
      data: JSON.stringify(data),
      contentType: 'application/json',
      url: '/api/auth/register'
    }).done(function(data){
      if(!data.ok){
        $('.message-register').text(data.error);
      }
    })
  }
});

$('#in').on('click',function(){
  var data = {
    login: $('#login').val(),
    password: $('#password').val()
    };
    console.log(data);
  $.ajax({
    type: 'POST',
    data: JSON.stringify(data),
    contentType: 'application/json',
    url: '/api/auth/login'
  }).done(function(data){
    if(!data.ok){
      $('.message-register').text(data.error);
    }
  })
});

The fragment with $('.reg-button').on works fine, but when I do it, but when it comes to $('#in').on('click', - error 500
Route Contents falls in the browser console log

const express = require('express'),
  router = express.Router(),
  bcrypt = require('bcrypt-nodejs'),
  models = require('../models');

//Регистрация
router.post('/register', (request, response)=>{
  const login = request.body.name,
    mail = request.body.email,
    pass = request.body.password,
    repass = request.body.repassword;
  if(!login || !mail || !pass || !repass){
    response.json({
      ok: false,
      error: 'Все поля должны быть заполнены!',
      fields: ['login', 'mail', 'pass', 'repass']
    });
  }else if(login.length < 3 || login.length > 16){
    response.json({
      ok: false,
      error: 'Длина логина от 3 до 16 символов!',
      fields: ['login']
    });
  }else if(pass !== repass){
    response.json({
      ok: false,
      error: 'Не совпадают пароль',
      fields: ['pass', 'repass']
    })
  }else{
    models.User.Users.findOne({where: {login:login}})
    .then(user=>{
      if(!user){
        bcrypt.hash(pass, null, null, function(err, hash){
          models.User.Users.create({
            login: login,
            mail: mail,
            password: hash,
            privilege: 1
          }).then(user => {
            response.json({
              ok:true
            })
          }).catch(err => {
            console.log(err);
          })
        }) 
      }else{
        response.json({
          ok: false,
          error: 'Имя занято!',
          fields: ['login']
        })
      }
    })
  }
});


//Авторизация
router.post('/login', (request, response)=>{
  сonsole.log(request.body);
})

module.exports = router;

that is, in fact, everything is the same, but for some reason it does not work in the case of login. What could be the problem?