That error is usually because of missing token in the ajax request.
Take a look here https://laravel.com/docs/5.8/csrf
Since you use axios, in the default app.js or maybe it's bootstrap.js that comes with laravel, it has this code:
window.axios = require('axios');
window.axios.defaults.headers.common['X-Requested-With'] = 'XMLHttpRequest';
let token = document.head.querySelector('meta[name="csrf-token"]');
if (token) {
window.axios.defaults.headers.common['X-CSRF-TOKEN'] = token.content;
} else {
console.error('CSRF token not found: https://laravel.com/docs/csrf#csrf-x-csrf-token');
}
As you can see it takes the csrf from the meta tag and appends all ajax calls with axios.
Edit: And if you use that code already, you probably just need the meta tag in your layout file:
<meta name="csrf-token" content="{{ csrf_token() }}">