Thanks for responding Aqibjaved.

I am assuming you have taken this note into account:

(Note:- Do not confuse instagram app id with facebook app id, your instagram app id is given inside Products > Instagram> Basic Display > Instagram App ID )

To make sure you are filling the correct details, make the curl request in terminal and check whether the same error persists:-

curl -X POST \

https://api.instagram.com/oauth/access_token \

-F client_id={instagram-app-id} \

-F client_secret={app-secret} \

-F grant_type=authorization_code \

-F redirect_uri={redirect-uri} \

-F code={authToken}

Source:

https://developers.facebook.com/docs/instagram-basic-display-api/getting-started