It's very common - and in fact I talk about it someplace near the beginning of this thread because it became a problem for me during the beta period - to find Windows 10 machines that can't run some or any Modern Style apps. This can also result in Windows Search breaking, the Start Menu refusing to open or even the Settings app refusing to open.
How common is it? If I had to guess, I've probably seen it 50 or 60 times now. Sometimes more than once on the same PC.
The easiest fix, which does not always work, is to use an Administrative Powershell session (bring up task manager, New Task, Powershell, tick the box for "run as admin") to run this command:
Get-AppXPackage | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
I've done that enough that I type it from memory.
Now, I've also found variations on that where there have somehow been changes to the file or registry ACLs that prevent that fix from working. Which is even more fun. You can say "But not one uses the modern Apps in the first place!" and you'd basically be right. Except that people DO use Start, Search and Settings and some people really like the Weather, News and Photos apps. I even know a few weirdos who actually like the Mail and Calendar.
It's a common problem. No one else has seen it?
