/var/log/httpd/access_log no longer being written
Solution 1:
Check the /etc/httpd/conf/httpd.conf and the files in /etc/httpd/conf.d for CustomLog directives and enssure that at least one exists that points to /var/log/httpd/access_log. Configure (or not) as required.
It's possible that you deleted/recreated the log file and failed to restart apache. In this case httpd will still be writing to the old log file (via the open file descriptor) - restart httpd to fix.
It's possible that the disk/partition is full.