Vue, Vuetify is not properly initialized

There is lot of changes with new version.

try this

import Vue from 'vue';
import Vuetify from 'vuetify';
Vue.use(Vuetify);

new Vue({
vuetify : new Vuetify(),
...
});

good luck

I do it this way (vue 3.9, vuetify 2.0)

In main.js (or App.js)

import vuetify from './plugins/vuetify'
...
new Vue({
  ...
  vuetify,
  render: h => h(App)
}).$mount('#app')

In plugins/vuetify.js

import Vue from "vue"
import Vuetify from "vuetify/lib"

Vue.use(Vuetify)

export default new Vuetify({
  icons: {
    iconfont: 'md',  // 'mdi' || 'mdiSvg' || 'md' || 'fa' || 'fa4'
  },
  theme: {
    dark: false,
  },
  themes: {
    light: {
      primary: "#4682b4",
      secondary: "#b0bec5",
      accent: "#8c9eff",
      error: "#b71c1c",
    },
  },
})

in App.vue

<template>
  <v-app>
    ...
  </v-app>
</template>