It appears as if this payer does not accept a claim that has dates of service in different months.
How Do I Resubmit This Claim?
From the EDI rejection page in Therabill, you will want to choose the option to Cancel the claim and then choose to send the sessions back to your bill insurance area. You will then need to go to your bill insurance area and create new claims (without choosing multiple dates of service across multiple months).
How to keep this from happening
When you create the claim in Therabill, when you get to the point where you choose which insurance card to submit to, put a check next to One date of service per claim. By doing so, Therabill will automatically split your claims for you for this payer.