This message will appear in a module when the payment settings have been setup, but has been set to 'Test Mode'.
While in 'test mode', the payment transactions are not actually posted to your 3rd party payment software system.
To take your system out os Test Mode, go to the Payment Settings section in the module and set the attribute for 'Credit Card Test Mode' = No
This means the program display settings have not yet been setup in the program module.
If this message appears on a form you are using but the field does not appear on your screen but there is an error message on the screen indicating the required field is missing, it is likely there is 'Display if' logic applied to the field but the 'Required' attribute on that field has been set to 'yes'.
Edit the field an ensure 'required' is set to 'No'. Set the field as required using the 'If selected, require' setting instead.