Unable to authenticate API Call

Unable to authenticate API Call

I am unable to hit the Access Token URL which according to the API documentation is  https://accounts.zoho.com/oauth/v2/token

I am using PostMan for my testing and I am able to get the Authentication Code but am unable to get the access token using the authentication code.
If I hit the above URL in a browser, I get the "Server Error Occured" error.

Anyone has any thoughts?

Thanks!