Cannot login after creating the user in SQL Server

SQL Server was not configured to allow mixed authentication. Here are steps to fix:

1. Right-click on SQL Server instance at root of Object Explorer,
2. click on Properties.
3. Select Security from the left pane.
4. Select the SQL Server and Windows Authentication mode radio button, and
5. click OK.
6. Open up Services and restart the SQL Service (SQLEXPRESS) Windows service.

Try setting your authentication mode to mixed mode. Your server does probably not accept logins using sql server accounts.

1. Open properties
2. Go to "Security"
3. Select "SQL Server and Windows Authentication mode"

Right click Server for properties...

properties