A user was unable to connect to Teradata from Toad DataPoint using a Microsoft Active Directory account. When I looked at the user account in Teradata, it was showing as active and unlocked.
The user was getting the following Logon Error:
[Teradata Database]  The UserId, Password or Account is invalid.
The user had her name, password, and server settings that were correct. It was the advanced tab for connection setting for connecting to Teradata that was the issues.
The Mechanism drop down menu is blank by default for new connections. Also, but not always, the Character set can be an issue. Pictured below is a default settings for a new connection to Teradata in Toad DataPoint.
The Mechanism needs to be set to LDAP & the Character Set needs to be set to ASCII. Once this was fixed, the user was able to connect to the Teradata database.