Login failed for user 'username'. The user is not associated with a trusted SQL Server connection.

Login failed for user 'username'. The user is not associated with a trusted SQL Server connection.

This error occurs if the SQL server has been configured to operate in "Windows Authentication Mode (Windows Authentication)" and doesn't allow the use of SQL accounts (e.g. sa, myuser etc). You can see KB article for same here..

This was happening because during installation, SQL Server Database Engine was set to Windows Authentication mode. This topic describes how to change the security mode after installation.