Try going through this list of solutions

Are you repeatedly getting the error “You need a new app to open this ms-windows-store” when trying to use the Microsoft Store in Windows 10? While this usually occurs due to a corrupted or missing Microsoft Store installation, an outdated app cache and conflicting settings can also cause the issue.

By going through the list of solutions below, you will be able to resolve the error relatively quickly in most cases.

If the Microsoft Store was working fine a moment ago, you're probably experiencing a minor technical glitch. Restarting your computer should help fix the problem, so try that before diving into the remaining solutions.