This is a terribly uninformative EDI rejection message that payers sometimes send back. Usually, when they send back this rejection message, they are supposed to follow it up with more information about what is missing. Unfortunately, sometimes they do not. If you do not see a follow up message, indicating what is making the claim unprocessable, then you may need to call the payer to find out why they are rejecting your claim.
MPORTANT: When calling the payer, make sure to let them know that the claim was EDI rejected. Usually, when you call, the first person you talk to is in the payers adjudication department. These people can only see claims that made it past EDI (were not EDI rejected). You may ask to talk to their EDI department or whoever handles EDI rejections. They will have a record of the rejection.