There can be multiple reasons for this depending on which element of the connection is turning down the connection. You have to look at the ODBC error diagnostics from SQLError(), SQLGetDiagRec() or SQLGetDiagField() to see where the connection is being turned down.
If the Easysoft ODBC-ODBC Bridge Client/Server has turned down the connection then you will get a messages similar to this:
28000:1:1326:[Easysoft ODBC (Client)] Invalid authorization specification
Here you should check the LogonUser and LogonAuth attributes of your client DSN. They should be a valid username and password for logging on to the server machine. This has nothing to do with the database engine.
See Why do I get "Invalid authorization specification" when LogonUser and LogonAuth are set to a valid username and password? where the error number (in the above case 1326) may be looked up.
If your database engine requires a username/password then these are specified as UID and PWD in the connection string or alternatively as the ODBC-ODBC Bridge attributes TargetUser and TargetAuth. Check your odbc.ini (.odbc.ini or the ODBC Administrator) to make sure these are valid for your database. Here is an example from MS SQL Server:
28000:1:18456:[Microsoft][ODBC SQL Server Driver][SQL Server] Login failed for user 'Fred'.
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