[Vuejs]-Vue.js dosen't render form's elements

I tried to reproduce your component. I guess you must define a few variables in you data property:

data () {
    return {
      validSignUp: false,
      signUpPasswordVisible: false,
      rules: [ (value) => !!value || 'This field is required' ],
      step: 1,
      registration: '',
      //...
    }
}