• On the server you are trying to connect your data source to have you checked the SQL log? It will give you a full description of the login failure and you can use the severity etc to find out the reason. Caveat is that auditing failed logins is turned on.

    Off the top of my head a couple of suggestions are:

    1. The login exists but has been set to deny connection

    2. The login exists but is disabled

    3. The login exists but is locked out.

    4. The SQL server has been changed to only accept windows authentication and not mixed mode.

    MCITP SQL 2005, MCSA SQL 2012