I'm running Windows 10 Pro Insider Preview Build 17063.rs_prerelease.171213-1610. Starting with the last release (I don't know the number. It was the one that I received immediately after that Fall release was official), the Windows Store (Is it called the Microsoft Store, now?) is completely missing. If I try to launch any Windows Store apps, they're missing as well. This includes the calculator and the feedback hub.
If I type "calc" into Cortana and click on the "Calculator+HD: Install App" that appears, I get the message: "You'll need a new app to open this: ms-windows-store". If I go into settings:Windows Insider Program and click on the "Give us feedback" link, it says "You'll need a new app to open this: feedback-hub"
I thought that perhaps the first preview after the Fall release had the store intentionally absent for updates. I it seems strange that it would still be missing with the latest update and that the Feedback Hub is missing from the Insider's Program.