In SSMS you need:
- Activate "SQL Server and Window Authentication mode"
- Create a user with all permissions, it must be used to create connection en PAD. NO use the same user "Window Authentication mode"

Maybe, check the Sql Server Configuration Manager:
- TCP/IP status must be Enabled

And the SQL Services should be like this:
- SQLEXPRESS: Running
- SQL Server Agent: Automatic
- SQL Server Browser: Running
