Below is my connection string:
connectionString=\"metadata=res://*/EDMX.Test.csdl|res://*/EDMX.Test.ssdl|res://*/EDMX.Test.msl;provider=System.Data.Sq
I saw this error when a colleague was trying to connect to a database that was protected behind a VPN. The user had unknownling switched to a wireless network that did not have VPN access. One way to test this scenario is to see if you can establish a connection in another means, such as SSMS, and see if that fails as well.