Typically seen with application to SQL DB authentication. You can find more detail out on Microsoft’s support web site but here are some things to look at just off the top:To increase security, the error message that is returned to the client deliberately hides the nature of the authentication error. However, in the SQL Server error log, a corresponding error contains an error state that maps to an authentication failure condition. Compare the error state to the following list to determine the reason for the login failure. State     Description   2   User ID is not valid.   5   User ID is not valid.   6  …