SQL Server: Login failed for SQL user

I had the free SQL Server 2019 Developer installed recently and tried to create SQL login and user. However, the new login couldn't be able to connect the server with the error: Login failed for user 'sennchiee'. (.Net SqlClient Data Provider).

To resolve this issue, connect SQL Server with Windows authentication and change the server authentication setting.

In the Object Explorer (usually on the left panel), right click on the server name and select properties. Select the security page and change the server authentication option to SQL Server and Windows Authentication mode.

Now restart the server for the change to be effective.

Once the server restarted, connect the server again with SQL login.

The SQL user connected successful now. =)