1. Make sure import setting is on:
    1. Tap the sidebar (top left button).
    2. Tap "Settings".
    3. Scroll down and tap "Siri/Apple Reminders".
    4. Turn the switch on.
  2. Make sure your default reminders list isn't connected to other 3rd-party software (e.g. Remember the Milk):
    1. Go to your iOS Settings app.
    2. Scroll down and tap "Mail, Contacts, Calendars".
    3. Tap through to each account and make sure that no account related to 3rd-party software has the Reminders setting on.
    4. If there is such an account, you'll have to turn off Reminders syncing on it.