I experience a weird issue on Magento ver. 18.104.22.168. The FPC was enabled in backend (Cache Management) but var/full_page_cache didn't exist. I figured out that app/etc/enterprise.xml was missing. After I restored it from a vanilla Magento installation the folder got created. But the size of the folder does not increase although I'm hitting several category and product pages:
du -sh full_page_cache/
It stays empty. I've already set the folder to 777 but no change.
Does anyone know what is may causing the issue?