Hi,

Have you selected the proper scope (global or site-specific) in the Event log listing?

You can check the Event log settings in Site manager -> Settings -> System - Log size whether it's greater than zero. This value doesn't express exact number of logs kept in the database. The older log events are deleted periodically, however not after each record addition, because that would waste system resources.
You can find more information about this process in the DevGuide Appendix C - Web config parameters
/ Event log settings
In case you won't find any problem and the issue persists, please let us know.

Regards,
Zdenek