Not able to generate OAuth token. Says Invalid redirect Uri.

Not able to generate OAuth token. Says Invalid redirect Uri.

I have been trying to generate the oauth token to make an API Call for using my ticketing system remotely from 3rd party. I am following all the steps thoroughly but still not able to generate the oauth token.

Firstly I made the Authorization Request using all the mandatory parameters as follows: 

Client ID : 1000.Z2QXxxxxxN9CQ35Oxxxxxxxxxxxxxx
Authorized Redirect URI : https://exinispl.com/
Scope : Desk.tickets.ALL
response type : code

After making call to this url I am not able to get the code in response which is needed to generate the oauth token.
The page says :   Invalid redirect Uri. URI passed does not match with the one configured. 

But I have not changed the redirect URL. So how is it possible that they are not matching.

I'm also sharing the Screen Shots for the same.
Please help me out.