They are referring to loop 2010BA which is the subscriber name loop on the EDI claim. They are specifically pointing to the insured's ID.
You will want to edit the primary ID (which is the insured's ID) on the insurance card for this client. Make sure it matches what is on the patients insurance card. If it does match, you may want to call the payer to verify eligibility, as it could be that the patient is no longer eligible or covered on the insurance plan.
Once you have edited the primary ID on the insurance card in Therabill, you can then click the Resubmit Electronically button at the top of the EDI rejection page in Therabill.