Are you running Laravel 7 or earlier? Try running composer dump-autoload after you've created a new factory.
edit nvm, looking at your code it seems you use Laravel 8.
edit 2. Did you upgrade from an older version of Laravel to Laravel 8? If so you have to update your composer.json file so it understands the location of your factories.
See the difference in the autoload key between L7 and L8.
https://github.com/laravel/laravel/blob/7.x/composer.json
https://github.com/laravel/laravel/blob/master/composer.json
it should look like:
"autoload": {
"psr-4": {
"App\": "app/",
"Database\Factories\": "database/factories/",
"Database\Seeders\": "database/seeders/"
}
},