This generic error can mean many things went wrong with your datastore connection.
First of all, I would recommend checking iSQL, Oracle DB, mySQL, or whatever the recommended database is that you are using. These systems will generate a more informative error message when attempting to login.
Below is a list of things to check:
Check that you have the proper ODBC driver installed.
Hostname
Database Name
Port #
Server Name
Username
Password
A quick way to check that you have the correct driver installed is the check the folder containing your Data Services bin.
On Windows systems, this may likely be held in:
Program Files (x86) -> SAP BusinessObjects -> Data Services -> bin -> ODBCDriversSelector.exe
This driver display will present to you the drivers that you currently have connected to Data Services.
Goodluck!