If you are unable to link Google Adsense Account to Google Analytics account, you might have to consider doing the following.
To be able to link Google Adsense Account to Google Analytics Account, the prerequisite is that you must have both Google Analytics or Google Adsense set to old version.
So open Google Analytics and click “Make old version Default”. Now similarly open Google Adsense and click “Make old version Default”.
Once you have done that:
1. Open Google Adsense.
In the overview page, click “Integrate Adsense to Analytics”.
2. Now follow the steps and you will be done with integerating the two accounts.
You can now access Adsense reports directly from Google Analytics.