[SOLVED] Piwik object is not accessible when using vueMatomo

I am using vuejs 3 and when I try to add VueMatomo I get the following error message:

Uncaught Error: [vue-matomo]: window.Piwik undefined after waiting for 3000ms (VueMatomo)

It worked fine the first time, but now I keep getting this message.

Here is my main.js file

import VueMatomo from 'vue-matomo';
//...
app.use(VueMatomo, {
  router,
  host: process.env.VUE_APP_MATOMO_HOST,
  siteId: process.env.VUE_APP_MATOMO_WEBSITE_ID
})

and in the component I am trying to track an event on a checkbox using MatomoTracker

import { MatomoTracker } from '@datapunt/matomo-tracker-js';
//...
this.matomoTracker.trackEvent('Checkbox', 'Click', this.$data.checked ? 'Checked' : 'Unchecked');