找不到Nuxt + Netlify Forms自定义成功页面

I have a simple Form in my Nuxt Project - hosting on Netlify and use the Netlify Forms feature - docs here https://www.netlify.com/docs/form-handling/

  <form
    action="/confirm" name="request" method="post" data-netlify="true" netlify-honeypot="bot-field"
  >
    <p class="hidden">
      <label>Don’t fill this out if you're human: <input name="bot-field" ></label>
    </p>
    <v-text-field
      label="Name"
      name="name"
    />
    ...
    <v-btn
      :disabled="!valid"
      type="submit"
    >send
    </v-btn>
  </form>

If I browse to https://mddomain.com/confirm it works fine.

If I submit the form on the first time I come to the /confirm page but Netlify doesn't safe the data. If i try it again I got this Error Mesage:

Page Not Found Looks like you've followed a broken link or entered a URL that doesn't exist on this site.

Back to our site

What's wrong with my code?