Part 1: Login to Microsoft SQL Server Management Studio, right click the instance -> Properties -> Connections -> Check “Allow remote connections to this server”.
Part 2: You also need to check on SQL Server Configuration Manager. This can found by click on “Start” -> All programs -> Microsoft SQL Server 2008 (may be different depend on your Microsoft SQL version) -> Configuration Tools -> SQL Server Configuration Manager.
After you open the Sql Server Configuration Manager, click on “SQL Server Services”, you will able to see a list of SQL services running on your server. Click “SQL Server Network Configuration” -> Protocols for MSSQLSERVER -> Right click “Properties” -> TCP/IP, make sure is enable. Double click on TCP/IP -> IP Address, make sure those IP address status is active and enable.