Here are some steps to follow if your calendar appointments and reminders are not showing up in Microsoft Outlook:

1. Verify that Outlook is connected to the internet.
2. Check to make sure Outlook is set to connect to the service that you are using for your calendar (e.g. Outlook.com, iCloud, etc.).
3. Close and re-open Microsoft Outlook.
4. Check your mailbox size limit and empty the Deleted Items folder if space is an issue.
5. Uninstall and re-install the Outlook software.