Hi Nordenstadt,
According to your description, firstly we need to ensure system has installed all updates, sometimes, incomplete update can cause Windows Store trouble.
Then, reboot computer and run App troubleshooter, get it from here.
http://windows.microsoft.com/en-us/windows-10/run-the-troubleshooter-for-windows-apps
Besides, please recall carefully what you have done before these app don’t work, to my knowledge, some third-part software that lead to software conflict also can cause current condition, clean boot is a check method.
Have a try.
Regards
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