Hi Ian,
Thanks for the added information. Yes, I confirm that the MCC account in the screenshot has standard access. However, I was referring to the MCC in which the client account mentioned in your SOAP logs is linked to (Kindly go Account Settings > Account Access of the client account). This MCC account is the one with the rejected access and also the one that appears to be managing your client account.
I also looked into the MCC account with the standard access and I could not see the client account that you are using in the list of accounts being managed by that MCC. Kindly make sure that the developer token and OAuth 2 credentials that you are using are that of the manager account in your screenshot. Additionally, I recommend that you link your client account to the MCC with the standard access through this
guide and use the credentials of that MCC to manage your client account in order to avoid getting the RateExceedError.
Also, I am unable to email you privately as I am receiving an error when I do. I am posting here in the forum instead and that is why I am unable to disclose the customer ids of the accounts I am referring to. If it is still unclear, please reply using Reply privately to author and include a separate email that I can use to contact you with.