As you might have noticed, you no longer have access to your pubCenter dashboard. You should be using Windows Dev Center to view Ads performance reports and manage your payout account and tax profile. Please do note that ads continue to serve as normal and your ad revenue will not be impacted.
Also, starting in January 2017, Microsoft will no longer serve banner ads to apps that use older advertising SDK releases from Microsoft. In order for your app to continue to receive banner ads in January 2017, you may need to update your app to use the latest advertising SDK and resubmit your app to the Store. To learn how to update your app manually, see the instructions here.
(For comparison with the table on that page, we are using WP8.0 (XAML) v220.127.116.11 and Win 8 (XAML) 18.104.22.168.)
Please be aware we will not be updating GameMaker: Studio to support the SDK for 8.1 platforms as Microsoft have already announced this will not be getting full support/further updates and we already support making UWP packages, and so accordingly the options currently presented for Windows 8 and Windows Phone 8 advertising in Global Game Settings will be removed as of this month's Early Access release. You are of course free to add support for alternative SDKs into your projects via your own extensions on Win8 and WP8 (and you will be able to add the updated Microsoft Advertising SDK yourself once you have this new EA).