Credentials pass the connection test and the credentials are confirmed (not by me though) to be valid in the database in question but I am still receiving the following messages:
May 24 10:02:32:792 sql_response: Profile: WS Notifications, operation: Execute SQL, COM Error [0x80004005] Unspecified error - [Microsoft OLE DB Provider for SQL Server] The server principal "(username)" is not able to access the database "dbname" under the current security context.
MS SQL Server is installed on the local server and is referenced with "localhost" in the profile.
This is related to the permissions and settings of the user for the database on the MS SQL Server side.
As a workaround, configure the local IP address or hostname instead of "localhost" in the probe and the error should be resolved.