Cannot Add Payment

Hello, we have added "Mollie API for Drupal" to an empty Drupal project, following the instructions and including the test key and organization access token as instructed. However, even though it allows us to add customers, it doesn't allow us to test the payment with the default form; it returns an error message saying, "An error occurred." How can we resolve this?

This is the error in the log:

Uncaught PHP Exception Drupal\Core\Entity\EntityStorageException: "An error occurred while creating the payment." at /var/www/vhosts/drupal9/web/modules/contrib/mollie/src/Entity/PaymentStorage.php line 125

In attach, the screen of the compiled form.