Windows Phone 8.1 users experiencing problems with the Store
Changing the system date will temporarily resolve the issue
Microsoft is committed to keep the Windows Phone 8.1’s Store live by July 11, 2018, while the OS itself is already out-of-support. But a number of users on Windows Phone 8.1 have reported an issue with the Store months before the deadline. An error code 80070020 is seen on the screen each time the user tries to download an app from the store. It’s probably a temporary server-side issue which should be resolved in the coming days. However, there is a simple and quick workaround if you experience this problem and want to download apps in this very moment.
Going to the Settings, and changing the system date to December 3, 2017 will allow you to download apps from the Windows Phone 8.1 store until the issue is officially addressed.
Microsoft is not yet pulling support for Windows Phone 8.1, but in the Summer many of the features and built-in apps may cease to work. At the same time, Windows 10 Mobile will remain fully supported until end of 2019 with cumulative fixes. Many of the built-in Windows 10 apps, and some of the third-party services, are still receiving updates in the Store, so Windows on Phone is not as dead as all specialists think.