It looks like you are submitting your claim with a legacy ID. The 2010AA loop they are referring to is the equivalent of Box 33B on the CMS-1500. Most payers do not want legacy ID's on claims. In fact, they are not supposed to request them since the NPI mandate.
If you are sending a legacy ID on the claim, you will want to remove it and then resubmit your claim.
Removing the Legacy ID from Box 33B
In Therabill, put your mouse over Billing in the top navigation bar and then click on Insurance List in the sub-navigation bar. You will now see a list of the insurance companies that you have listed on insurance cards in Therabill. Find the insurance company in this list (use the search filter at the top of the list to help you find it). Once you have found the insurance company, click the Manage link associated with the insurance company. This will open up the manage insurance company form. At the top, click the Box 33 tab. At the bottom of the Box 33 section, you will see a small area labeled "Box 33B". Remove the information you have from the Box 33B area and then click the Save Changes.
Resubmitting the claim
From the EDI rejection page in Therabill, click the Resubmit Electronically button at the top of the page. This will send the claim out again with the current information.