VueJS: components not rendering

I'm going through my first Vue tutorial and am a bit stuck. I've got an App.vue file, which I can see with the browser inspector extension is loading, a router index.js file, and login/signup forms. I can see the default Hello component.

I should be able to go to /login and /signup, but the components do not load. There are no console errors. Where do I begin troubleshooting?

App.Vue:

<template>
  <div id="app">
    <router-view/>
  </div>
</template>

<script>
export default {
  name: 'app'
}
</script>

<style>
  body {
    background-color: #f7f7f7;
    padding-top: 50px;
    padding-bottom: 50px;
  }

  .is-danger {
    color: #9f3a38;
  }
</style>

Router index.js file:

import Vue from 'vue'
import Router from 'vue-router'
import HelloWorld from '@/components/HelloWorld'
import SignUpForm from '@/components/Auth/SignUpForm'

Vue.use(Router)

export default new Router({
  routes: [
    {
      path: '/',
      name: 'HelloWorld',
      component: HelloWorld
    },
    {
      path: '/signup',
      component: SignUpForm
    }
  ]
}))

SignUpForm.vue:

<template>
  <div class="ui stackable three column centered grid container">
    <div class="column">
      <h2 class="ui dividing header">Sign Up, it's free!</h2>

      <Notification
        :message="notification.message"
        :type="notification.type"
        v-if="notification.message"
      />

      <form class="ui form" @submit.prevent="signup">
        <div class="field" :class="{ error: errors.has('name') }">
          <label>Full Name</label>
          <input type="text" name="name" v-model="name" v-validate="'required'" placeholder="Full name">
          <span v-show="errors.has('name')" class="is-danger">{{ errors.first('name') }}</span>
        </div>

        <div class="field" :class="{ error: errors.has('username') }">
          <label>Username</label>
          <input type="text" name="username" :class="{'input': true, 'is-danger': errors.has('username') }" v-model="username" v-validate="'required'" placeholder="Username">
          <span v-show="errors.has('username')" class="is-danger">{{ errors.first('username') }}</span>
        </div>

        <div class="field" :class="{ error: errors.has('email') }">
          <label>Email</label>
          <input type="email" name="email" :class="{'input': true, 'is-danger': errors.has('email') }" v-model="email" v-validate="'required|email'" placeholder="Email">
          <span v-show="errors.has('email')" class="is-danger">{{ errors.first('email') }}</span>
        </div>

        <div class="field" :class="{ error: errors.has('password') }">
          <label>Password</label>
          <input type="password" name="password" :class="{'input': true, 'is-danger': errors.has('password') }" v-model="password" v-validate="'required'" placeholder="Password">
          <span v-show="errors.has('password')" class="is-danger">{{ errors.first('password') }}</span>
        </div>

        <button class="fluid ui primary button" :disabled="!isFormValid">SIGN UP</button>

        <div class="ui hidden divider"></div>
      </form>

      <div class="ui divider"></div>

      <div class="ui column grid">
        <div class="center aligned column">
          <p>
            Got an account? <router-link to="/login">Log In</router-link>
          </p>
        </div>
      </div>
    </div>
  </div>
</template>

<script>
import Notification from '@/components/Notification'

export default {
  name: 'SignUpForm',
  components: {
    Notification
  },
  data () {
    return {
      name: '',
      username: '',
      email: '',
      password: '',
      notification: {
        message: '',
        type: ''
      }
    }
  },
  computed: {
    isFormValid () {
      return Object.keys(this.fields).every(key => this.fields[key].valid)
    }
  },
  beforeRouteEnter (to, from, next) {
    const token = localStorage.getItem('tweetr-token')

    return token ? next('/') : next()
  },
  methods: {
    signup () {
      axios// eslint-disable-line no-use-before-define
        .post('/signup', {
          name: this.name,
          username: this.username,
          email: this.email,
          password: this.password
        })
        .then(response => {
          // save token in localstorage
          localStorage.setItem('tweetr-token', response.data.data.token)

          // redirect to user home
          this.$router.push('/')
        })
        .catch(error => {
          // display error notification
          this.notification = Object.assign({}, this.notification, {
            message: error.response.data.message,
            type: error.response.data.status
          })
        })
    }
  }
}
</script>

My main.js file:

// The Vue build version to load with the `import` command
// (runtime-only or standalone) has been set in webpack.base.conf with an alias.
import Vue from 'vue'
import App from './App'
import router from './router'
import axios from 'axios'
import VeeValidate from 'vee-validate'

window.axios = axios
axios.defaults.baseURL = 'http://127.0.0.1:3333'

Vue.config.productionTip = false
Vue.use(VeeValidate)

/* eslint-disable no-new */
new Vue({
  el: '#app',
  router,
  components: { App },
  template: '<App/>'
})