Did you configure Usage Collection from the SharePoint Central Admin.
Central Administration > Monitoring > Configure usage and health data collection
Enable usage data collection (is checked)
Events to log:
Content Import Usage
Content Export Usage
Page Requests (This option must be checked)
Search Query Usage
Site Inventory Usage
After you enable Web Analytics , SharePoint automatically does not start making analytical data unless we specify data that needs to be captured and saved on the analytics service application database.
SharePoint will created a service application database typically named as "WSS_Logging" after you provision Usage Collection Service.
If this service is already present , then I would suggest to reconfigure usage and logging service once again. It should work.