There are usually two causes for the above error:
The SQL Server does not have SQL Authentication turned on. A trusted SQL Server connection implies that the account the agent is running under (LocalSystem by default) has appropriate permissions in SQL Server. This is usually not the case.
The SQL Server does not have an eventsentry_svc account, and/or no EventSentry database exists. This usually happens when you are pointing EventSentry to the wrong instance on a server when multiple instances exist.
You can troubleshoot this problem as follows:
1a. Make sure that your SQL Server is configured to allow both Windows Authentication and SQL Authentication. See the first additional link below for more information.
1b. If, for some reason, you cannot configure your SQL server to SQL Authentication, then you need to reconfigure the EventSentry service to run under a Windows account that has permissions to write to the EventSentry database. You will need to make this change on every computer that is running the EventSentry agent. To accomplish this, open the Services control panel under Administrative Tools, right-click the EventSentry service and click the Log On tab. There, specify a user account that has both administrative rights on the local machine and write access to the EventSentry database.