Please check the following three possible causes:
1. If you are running IDKit PRO SDK and ExpressID AFIS on two different computers, the ODBC data source has to be configured on the PC where ExpressID AFIS is installed.
2. When creating a DSN, make sure you are creating a System DSN, not User DSN. User DSNs are not visible to services running in background.
3. Every database server provides an option to test the ODBC connection in the DSN configuration window. This test should be performed before testing the connection with ExpressID AFIS.