After you subscribe to a filtering service, appliance-based filtering doesn't start until a rating list is successfully downloaded from the filtering service. The appliance will not download the rating list until you check Enable in the Service List. (See Filtering Tab.)
The PICS description file, which normally downloads immediately after the service is defined and which you use to configure your service, contains only category names. It does not supply the data required for content filtering.
The initial download process can take several minutes to complete. During this time, content filtering might be enabled, but it is not effective. Filtering begins immediately after the initial rating list is downloaded.
Subsequent downloads are made directly into memory so that the changes to the filtering list are effective immediately.
Each time an appliance starts up, content filtering doesn't begin until the rating list is loaded into appliance memory. Because rating lists can be quite large, the memory-loading process can require up to one minute to complete.
Also, new rating lists are downloaded each time the appliance is restarted. The appliance will repeat a download request on the quarter hour (at 12:00, 12:15, 12:30, and so on) until the download is successful.
If you remove a defined service for whatever reason and then reinstall it, you should verify the next rating list download time. It might be set for the next day, leaving your network without appliance-based filtering until the download is completed and the filter file is loaded into memory.