Hi,
This issue could be related to corrupt Store settings. This might also occur if Windows 8.1 update is not installed properly.
Are you having the same issue while using any other apps apart from Store?
I would suggest you to check for the current version of Windows using the following steps:
a) Press Windows and X key together and select System.
b) Check for the version of Windows showing up under System Properties.
You can follow the steps to reset Windows Store cache memory and check if it resolves the issue:
a) On the desktop screen, press Windows and R key to open run box.
b) Type WSReset.exe and hit Enter.
Please get back to us with the status of this issue.