Please make sure the below are well configure:
Other possible reasons:
1. if the above are configured well and still prompt the same error, Please check if SQL Server is actually using port 1433. It may be using something other than the default port. - http://stackoverflow.com/questions/19451490/how-to-identify-port-number-of-sql-server
2. If choose a named instance and you call your named instance SSQDatabase1 and your pc's name is PCX1. You must enter PCX1\SSQDatabase1 not just SSQDatabase1 or you will receive the named pipes error.
3. I spent about an hour trying to figure out what's wrong with SERVER/INSTANCENAME when everything is configured correctly, named pipes, user access rights... and suddenly it struck me, it's not a slash, it's a backslash (\).
The horror, the shame..