Hello EthanC712,   Thank you for reaching out to Constant Contact API Developer Support.    Based on our logs, it looks like you may have already resolved your issue, but here is what I was able to find:   It looks like at the time that you posted this, you may have been making  a GET call to the /account/summary endpoint to get a summary of account details for a specific account. Since this is not a Partner endpoint, it requires that each individual account you are requesting info for has granted access to the updated version of your application and has been granted its own unique token set.   Get Account Summary Details https://v3.developer.constantcontact.com/api_guide/account_details_get.html   To get account info for an account managed under your partnership, you would instead want to make a GET call to the /partner/accounts/{encoded_account_id}/plan endpoint to get billing details for a single client account.   Get Billing Plan Details for a Client Account https://v3.developer.constantcontact.com/api_guide/partners_plans_get.html   If you have any other questions regarding updating your app to our new authorization management service, I’ll be sending a follow-up email to the email address we have on file for your account that you can reply to directly for high priority assistance.    If you did not receive the email or need it sent to another address, please email us directly at webservices@constant contact.com or contact our support team via phone and reference case number #29714936 and provide the best contact email for you so that we can follow up in an expedited manner.   Please have a look and let us know if you have any other questions! ... View more