This rejection states that the submitted subscriber ID did not meet the required formatting for submitting to Blue Cross Blue Shield (BCBS). As a general rule, all BCBS payers have a 3-alpha character prefix included in the subscriber ID. The prefix is also state specific. If this rejection message is received it either means that the submitted subscriber ID did not have the required prefix, or the prefix was invalid for the submission. Check the patient's insurance card to verify the subscriber ID was entered correctly.
A comprehensive list of BCBS prefixes can be found HERE.