On January 1st, 2018, Sitecore turned off the Google AdSense and Google Analytics applications that are available through the Sitecore App Center.
The shutdown date is directly connected with the date when Mainstream Support ends for the latest Sitecore XP release (7.5) supporting the apps. For more information, please read the Product Lifecycle and Modules Compatibility articles.
This applies to all versions of Sitecore App Center.
You have not been able to activate the Google AdSense and Google Analytics apps from the App Center since November 2017.
For the existing customers, the related functionality might continue working even after January 1st, 2018. However, you must reconfigure your Sitecore solution to eliminate dependencies on Sitecore Tag Management and the related apps. Please refer to the original Tag Management library documentation to get more details on the anticipated changes.