I can't find my debit orders under Fee order history. Why could this be?

There are two different views depending on the authentication you use to sign in. 

If you sign in with two-factor authentication, you will see all payments (credit card, bank transfer and deposit account) that were submitted using this sign-in method. 

If you sign in with your email address and password, you will see all payments (credit card, bank transfer) that were submitted using this authentication method. 

The same applies for rejected payments. Please also bear in mind that the Fee order history is always user-specific, no matter which sign-in method you use.