When using Database Mirroring for SQL Server, the default connection method using SQL Native Client will not work because it assumes a specific database instance where the Automic database is available.
Change its SQL Pull Adapter to ODBC connection by performing the following steps:
1) open Modelling Studio
2) in the EventBase Panel, expand Data Sources and double click Automic Data Source to show its properties
3) in the Properties Panel you will see the connection string, click on the [...] and in the opening dialog, unlock the connection string and replace it with a correct ODBC connection string which contains only the User DSN and no specific database instance. Also switch to "Microsoft SQL Server" / "ODBC" instead of "Microsoft SQL Server"/ "Native Client".
4) Test the connection to ensure that the ODBC connection is properly set up, if yes press 'OK' in the dialog to save these changes
5) In EACH of the Sql Pull Adapters which use the Automic Data Source, open its properties and replace the occurence of the delimiter parameter (usually @param) with '?' both within the SQL query and the QueryDelimiter parameter.
6) save eventbase to apply changes