Plugin not working on manual payment page?

Hi,
I created a new order manually in Woocommerce because the wanted product is not published in our webshop (with good reasons).
In my order in the Woocommerce backend, I have a link which leads directly to an order summary page plus the possibility to pay the order. With other payment methods, I can send this link to the customer and he/she can pay for the order I manually created without being forced to enter the checkout.
But with Easycredit, there is always an error message that the shop is not correctly configured.

However, the “normal” payment within the checkout works.
I activated the “Debug Logging” – but where is the log file for Easy Credit?
Best regards,
Christoph