This error message means that your payment method is not connected to a bank account.
To fix this, navigate to 'Payment methods' in the Admin Settings and select your payment method. From there, you can link it to your bank account (see screenshot below).
How to add a bank account in Xero:
1. In the Accounting menu, select Bank accounts.
2. Click Add Bank Account.
IMPORTANT: Once you have added your bank account or credit card in Xero, the next step is to synchronize it with Rydoo. Navigate to Admin > Integrations > Select the Branch > Click "synchronized". Once this has been completed, be sure to link it to the appropriate payment method.