The request can be rejected due to multiple reasons:
Risky business category: The respective payment method (lets say, Trustly) is not comfortable with your business model.
Incorrect account details: The banking partner rejects your request if you have provided any incorrect information at the time of your application.
Unupdated website: The customer-facing website is thoroughly checked by our banking partners. The banking partner can reject your request if the website is not updated or has a limited information, including details such as Terms & Conditions, Delivery timelines, Refund & Cancellation policies and so on.