Microsoft stopped work on Windows Phone 8.1 back in July 2017, meaning that phones running the outdated OS no longer got software updates. Now the company is preparing to pull the plug completely and shut down the app store. Starting on December 16 2019, Windows Phone 8.1 users will no longer be able to download apps. Note that this means any app, even ones you already have - if you uninstall an app or reset your phone, there will be no way to get the app back. Also, apps will not receive updates. It's possible that some will suffer degraded functionality as Microsoft's services are...
Source: https://www.gsmarena.com/microsoft_will_pull_the_plug_on_windows_phone_81s_app_store_on_in_middecember-news-39660.php
