firebaseでdisplayNameを取得したい

firebaseにてdisplayNameを取得しようとしているのですが、displayNameがnullになり、取得ができないです。
displayNameをfirebaseに登録する処理が間違っていると思うのですが、どこが間違っているかわからないです。ご教授よろしくお願いします。

js
1store.js
2
3
4import Vue from 'vue';
5import Vuex from 'vuex';
6import firebase from './plugin/firebase.js';
7import router from './router.js';
8
9Vue.use(Vuex);
10
11export default new Vuex.Store({
12  state: {
13    userName: '',
14    email: '',
15    password: '',
16  },
17  getters: {
18    email(state) {
19      return state.email;
20    },
21    password(state) {
22      return state.password;
23    },
24    userName(state) {
25      return state.userName;
26    },
27  },
28  mutations: {
29    setEmail(state, email) {
30      state.email = email;
31    },
32    setPassword(state, password) {
33      state.password = password;
34    },
35    setUsername(state, userName) {
36      state.userName = userName;
37    },
38  },
39  actions: {
40    registerUser({ commit }, userInfo) {
41      firebase
42        .auth()
43        .createUserWithEmailAndPassword(userInfo.email, userInfo.password)
44        .then((response,userInfo) => {
45          // commit('setUsername', user.userName);
46          response.user.updateProfile({
47            displayName: userInfo.userName,
48            // displayName:state.userName
49            // displayName:user.userName
50          });
51          console.log(response);
52          const user = firebase.auth().currentUser;
53          commit('setEmail', user.email);
54          commit('setPassword', user.password);
55          commit('setUsername', user.userName);
56          router.push('/Home');
57        })
58        .catch((e) => {
59          console.log(e);
60        });
61    },
62    logIn({ commit }, userInfo) {
63      firebase
64        .auth()
65        .signInWithEmailAndPassword(userInfo.email, userInfo.password)
66        .then((response) => {
67          const user = firebase.auth().currentUser;
68          commit('setEmail', user.email);
69          commit('setPassword', user.password);
70          console.log(response);
71          // router.push('/Home');
72          console.log(firebase.auth().currentUser.displayName);
73          // console.log(firebase.auth().currentUser.displayName);
74        })
75        .catch((e) => {
76          console.log(e);
77        });
78    },
79  },
80});
81

displayNameを表示させる

vue
1<template>
2  <div>
3    <p>{{userName}}さんようこそ!!</p>
4  </div>
5</template>
6
7<script>
8import firebase from '../plugin/firebase.js'
9export default {
10  data() {
11    return {
12      userName:firebase.auth().currentUser.displayName,
13    }
14  },
15}
16</script>
17

会員登録のコード

vue
1<template>
2  <div>
3    <div>
4      <h1>新規登録画面</h1>
5    </div>
6    <form @submit.prevent="signUp()">
7      <div>
8        <label>ユーザ名</label>
9        <input
10          type="text"
11          v-model="userInfo.userName"
12          placeholder="userName"
13          class="text"
14        />
15      </div>
16      <div>
17        <label>メールアドレス</label>
18        <input
19          type="email"
20          v-model="userInfo.email"
21          placeholder="E-mail"
22          class="email"
23        />
24      </div>
25      <div>
26        <label>パスワード</label>
27        <input
28          type="text"
29          v-model="userInfo.password"
30          placeholder="Password"
31          class="password"
32        />
33      </div>
34      <button class="register" type="submit">新規登録</button><br />
35    </form>
36  </div>
37</template>
38
39<script>
40export default {
41  data() {
42    return {
43      userInfo: {
44        email: '',
45        password: '',
46        userName: '',
47      },
48    };
49  },
50  methods: {
51    signUp() {
52      this.$store.dispatch('registerUser', this.userInfo);
53    },
54  },
55};
56</script>
57
58<style scoped>
59.text,
60.email,
61.password {
62  border: 1px solid;
63}
64ul li {
65  list-style: none;
66}
67.email {
68  margin-right: 47px;
69}
70.password {
71  margin-right: 18px;
72}
73label {
74  text-align: center;
75}
76.register {
77  border: 1px solid;
78  background-color: white;
79  color: blue;
80  outline: none;
81}
82</style>
83