I have this DatabaseSeeder.php:
Step one - generate seed:
php artisan make:seed MemberInvitationSeeder
Step two - In DatabaseSeeder.php add line:
$this->call(MemberInvitationSeeder::class);
Step three:
composer dump-autoload
Step four:
php artisan db:seed
This should work
If this isn't the clue, check the composer.json file and make sure you have code below in the "autoload" section:
"classmap": [
"database"
],