Hi Lesli,
This issue might occur if the version of Mail and Calendar app is outdated or corrupt.
First of all, check if there are updates pending for such apps in Store.
Follow the steps mentioned below to check for updates under Store:
- Type “store” and click on Store.
- Look for the notification for pending updates available at the top right corner of the store. If yes, click on “updates” to check for the list of updates available.
- By default, all the updates for the apps would be marked. Right Click on the apps window and select “Install updates”.
- Wait for all the updates to get installed.
If the issue still persists, proceed with the troubleshooting methods provided below:
Method 1:
Refer to the link and run the Modern User Interface app troubleshooter:
Check if that fixes the issue. If not, refer to the section “Solution 3: Uninstall and reinstall the app”.
If the issue still persists, proceed to the next method.
Method 2:
Let’s run SFC scan and check if it finds and fixes corrupt system files.
Refer to the link to run SFC scan:
Follow the steps from section "Windows 8.1 or Windows 8":
http://support.microsoft.com/kb/929833/en-us
Please reply to us with the status of this issue.