Some products install a hidden SQL server instance (usually express edition). If you check in Sql Server Configuration Manager, you can see SQL instance name like ‘MICROSOFT##SSEE’. But if you want to connect to it using SSMS (SQL Server Management Studio), you won’t be able to connect to it because the instance is set to hidden. Sometime, we have to connect to it to do some maintenance work as a DBA. So here is the way to unhide it. In SQL Server Configuration Manager, expand SQL Server Network Configuration, right click on “Protocols for MICROSOFT##SSEE”, choose Properties from the context menu. In the Flags tab of the Properties dialog, you can see the Hide Instance flag is “Yes”, just set it to “No”. Please see the following screen shot.
You have to restart the SQL server service for this instance to make this flag effective. You will be able to connect to it in SSMS successfully now. Cheers!