Magento2 implements CyberSource Secure Acceptance Method and you must configure CyberSource with Profile ID, Merchant ID, Transaction Key, Access Key and Secret Key.
I have tested CyberSource with our sandbox account and it's work as expected.
Please ask merchant try to follow next steps: Goto sandbox account https://ebctest.cybersource.com
Tools & Settings -> Profiles -> Select your profile
Press Open Editable Version -> Customer Response Pages and enter URL like https://your-host.com/cybersource/SilentOrder/TokenResponse