Fatal error: Uncaught Error: Class "Symfony\Component\Serializer\Normalizer\AbstractNormalizer" not found in /var/www/crm_killing_ninja/vendor/symfony/serializer/Normalizer/JsonSerializableNormalizer.php:24 Stack trace: #0 {main} thrown in /var/www/crm_killing_ninja/vendor/symfony/serializer/Normalizer/JsonSerializableNormalizer.php on line 24