There was a short period of time when the FreePBX Distro was incorrectly setting up the logfile system, and so no logs were being generated. It only lasted a very short period of time (a week or less), and it was several months ago.
If you just happened to install your system at that time, then you’re system isn’t configured to create logs. You’ll need to learn how to configure the logging system, or do a fresh install and start over.
Otherwise, I don’t know, but it probably is a similar issue, i.e. logging system not configured.