Specflow feature file.cs is not generating

Generation error: Unable to load plugin assembly:

C...\packages\Baseclass.Contrib.SpecFlow.Selenium.NUnit.1.3.1\tools\Baseclass.Contrib.SpecFlow.Selenium.NUnit.SpecFlowPlugin.dll.

-> Could not load file or assembly

'file:///C:...\packages\Baseclass.Contrib.SpecFlow.Selenium.NUnit.1.3.1\tools\Baseclass.Contrib.SpecFlow.Selenium.NUnit.SpecFlowPlugin.dll' or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)

=> An attempt was made to load an assembly from a network location which would have caused the assembly to be sandboxed in previous versions of the .NET Framework. This release of the .NET Framework does not enable CAS policy by default, so this load may be dangerous. If this load is not intended to sandbox the assembly, please enable the loadFromRemoteSources switch.

Did you install the SpecFlow-Selenium-Nunit package through NuGet? Messages like this occur when you download and install plugins manually without enabling the load of resources from external sources. You can enable it by setting the loadFromRemoteSources property in your project options.