Try the following:
Check that you added an email account that has an integrated calendar. Some accounts might not include a calendar feature.
You might need to refresh your calendars. In the Calendar app, swipe down from the top of the screen. Tap .
If you imported calendar entries using BlackBerry Link, you might see duplicate entries on your device after syncing your device and computer.
You can remove duplicates by deleting duplicates in your address book, or by clearing your local data on your device.
To remove duplicate calendar entries by deleting your local device data, do the following: