A CO-97 denial code means that the line item denied is being bundled into another service rendered on that same DOS, or another service from a previous DOS that the patient is in a global period for. If the line item that denied is unrelated to services on that same DOS, or previous DOS, and can be billed separately, then a modifier is needed to indicate this. But as others said, without knowing what else was billed, there is no way to advise you on what to do next.