Problem:

You are going to install Json.NET NuGet package but you get the following error:

 JSON Failed to initialize the PowerShell host. If your PowerShell execution policy setting is set to AllSigned, open the Package Manager Console to initialize the host first.

Solution:

1. Open PowerShell console in Administrator mode. Note that you should open the x86 version if you are running the 32bit version of Visual Studio. Likewise open x64 if your Visual Studio is 64bit.
2. Run this command start-job { Set-ExecutionPolicy Unrestricted } -RunAs32 | wait-job | Receive-Job
3. Reopen Visual and the issue should be fixed