Access token is invalid

[KresimirG9]

I finished with registering my app, and getting api key and client secret. I downloaded example from git hub for .net, and I built a small web application in asp.net mvc4, that is using CTCT_wrapper project from the sample.
https://github.com/constantcontact/.net-sdk
I am calling 'AuthorizeFromWebApplication' method that redirects to constanct contact login page. After I enter credtials, and grant access, on my redirection URL i get the access token. This works fine, but if I try to invoke any method, it throws an exception that my access token is invalid.
Why this happens ??
Also, if I generate access token on this link
https://constantcontact.mashery.com/io-docs for the same api key, and same credentials i get different access token, and I can invoke any method with that access token..
Please could you help me to figure out what am I doing wrong ?

[KresimirG9 · Accepted solution]

I figured it out that I got the authorization code, and after that I called method 'GetAccessTokenByCode' using the authorization code that I recieved.