1. Check that you have the latest version of Outlook installed on your computer.
2. Make sure that your Office package is up-to-date by ensuring that all Office applications have been updated as necessary.
3. Check and make sure that you are connected to the internet and that your computer is not experiencing any network issues.
4. Ensure that you have necessary permissions to change the font settings.
5. Log out and back in to see if settings are updated correctly.
6. Modify your registry values, or delete any conflicting values.
7. Check that your fonts haven’t been corrupted or damaged.
8. Move the font files you wish to use from the original folder to the Windows Fonts folder.
9. Try selecting multiple font types within the Options menu and then click the OK button.
10. If all else fails, you may need to reinstall Outlook.