Click your Start Button, then just type cmd and on the resulting list, right click Command Prompt and select 'Run as Administrator'.
Run this command and press Enter:
wsreset -i
Wait for that command to complete, then close Command Prompt and restart your PC, then check if the store is working correctly.
If not, open the Settings App, go to System - Recovery, and click the Reinstall Now' button in the 'Fix problems with Windows Updates' section, then wait for that process to complete.