Claims denied because of "box 41" information missing

I saw that there was a post on this about a year ago, but am wondering if anybody has any direct guidance on what I need to do to fix the issue.  I am only having this issue with one insurance carrier/payer, all other claims are going through fine.  But this payer is denying my claims and saying that I'm not an in-network provider as the reason for the denial (I confirmed I am in-network), and that they're saying this because there is "no provider information in box 41 on page 2 of the claims" that I am submitting.  All of my information is entered into boxes 24 and 33 on the claims I'm submitting through SP.  I have been billing as an individual - should I be billing as an organization?  What do I need to do to make sure that my provider information (name, contact, NPI, taxonomy) shows up for the payer when I send the claims?  Thank you for any guidance!