Recently I built a fresh virtual environment to do some testing. After installing Microsoft SQL Server 2017 I started Microsoft SQL Server Management Studio. After specifying servername and instance name I couldn’t connect. The first thing I checked was the firewall. To determine if the firewall was giving problems I completely disabled it temporarily. After disabling I still couldn’t connect:
Cannot connect to sql01\sql2017.
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 – Error Locating Server/Instance Specified) (Microsoft SQL Server, Error: -1)
So the second thing I did was starting the SQL Configuration Manager and I immediately found the problem: The SQL Server Browser wasn’t started! After starting the service I could connect. Please remember: when you are running SQL in a named instance, SQL Server Browser is neccesary to connect. More information about the SQL Server Browser Service can be found on Techet: https://technet.microsoft.com/en-us/library/ms181087(v=sql.105).aspx