Hi Gibs. I'm Greg, an installation specialist, 10 year Windows MVP, and Guardian Moderator here to help you.
Try repairing the Calculator at Settings > Apps > Apps & Features > Calculator > Advanced Options > Reset.
If that isn't enough then re-register the app from Option Two here:
http://www.tenforums.com/tutorials/3175-apps-re...
I hope this helps. Feel free to ask back any questions and keep me posted. I will keep working with you until it's resolved.
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