No Username-Field on Login-Page

Hallo!
Im trying to get the login working, but I have the problem, that on the LoginPage there is no field for the username!

This is my login form.de.md:

---
title: Login
visible: false
login_redirect_here: false
forms:
    login:
        action: null
        method: post
        fields:
            username:
                type: text
                id: username
                placeholder: PLUGIN_LOGIN.USERNAME_EMAIL
                label: PLUGIN_LOGIN.USERNAME_EMAIL
                autofocus: true
            password:
                type: password
                id: password
                placeholder: PLUGIN_LOGIN.PASSWORD
                label: PLUGIN_LOGIN.PASSWORD
    login-twofa:
        action: null
        method: post
        fields:
            2fa_instructions:
                type: display
                markdown: true
                content: PLUGIN_LOGIN.2FA_INSTRUCTIONS
            2fa_code:
                type: text
                id: twofa-code
                autofocus: true
                placeholder: PLUGIN_LOGIN.2FA_CODE_INPUT
---

<p># User Login</p>