Check whether you connect it via iCloud option or not. If you connect it via iCloud option and you want to import flights, connect it via IMAP option in the app's settings.
This would allow us to import flight from your iCloud email. In Host enter imap.mail.me.com
Note: Please check that you input username just only here. This is usually the name part of your iCloud email address (for example, emilyparker, not firstname.lastname@example.org). If your email client can't connect to iCloud using just the name part of your iCloud email address, try using the full address.
If you connect it via IMAP option but still don't see flights, check this article.