I am new to NopCommerce as well as C# MVC. I am working on NopCommerce 3.80.

As per Instructions I downloaded Google+ Plugin from [NopCommerce Official site](http://www.nopcommerce.com/p/2179/google-external-authentication.aspx) and Installed it and also configured it.

But when i click on Login with google button, it shows an error of 

> 
> Google OAuth 2 authorization - Error: redirect\_uri\_mismatch
> 
> 
> 

[![enter image description here](https://i.stack.imgur.com/7n3qd.jpg)](https://i.stack.imgur.com/7n3qd.jpg)

Can anybody help me to solve this ?

And another Question is do I have to create a Class Library for the External Authentication as like Facebook(Inbuilt Plugin) ??