You should try to add at the beginning of your app.php file:
phpinfo();exit;
And then look that apc is correctly enabled
Also look at your PHP errors (/var/log/...)
And eventually check that your config_prod configuration has apc enabled, something like:
framework:
validation:
cache: apc
doctrine:
orm:
metadata_cache_driver: apc
result_cache_driver: apc
query_cache_driver: apc