After installing the EventSentry agent on computers when I try to start the EventSentry service (agent), I receive the error "The system license has expired. Your logon request is denied."

This message is displayed when the EventSentry agent does not have a valid license installed, it does not necessarily mean that a trial license has expired.

First, try to push the configuration to the remote computer(s) again, by right-clicking the group and selecting "Update Configuration". Then, right-click the group again and select "Manage Agent(s) -> Start" or try to start the EventSentry service manually.

If this still does not work, check to see if the file eventsentry_svc.reg file is present in the %SYSTEMROOT% of the remote computer.

If it is not, then you might have software installed that is preventing this file from being copied there by the management console. A feature in newer versions of McAfee does block files from being copied to the %SYSTEMROOT% directory from a remote location, so you will have to disable this feature (Access Protection -> Anti-virus standard protection -> Prevent remote creation/modification of executable and configuration files) in order to use Remote Update or setup the ES$ share instead (see additional links below).