Qualtrics - Mailinglist contacts API

Hi folks, Are there any known issues with the mailing list contacts API? Im trying to pull the contacts out of a mailing list but getting an "Invalid mailinglistid" when I try. Im fairly sure the mailinglistid is fine as it is returning the correct result on a direct mailing list query. Summary of process below with a made up mailinglist id Run https://yourdatacenterid.qualtrics.com/API/v3/mailinglists/CG_ABC12345678 Get a correct JSON response including the name etc. Run https://yourdatacenterid.qualtrics.com/API/v3/mailinglists/CG_ABC12345678/contacts Get an error back including httpStatus:400 - Bad Request, errorMessage:Invalid mailinglistId., errorCode:GPR_1 Im not sure how/why I can get an invalid mailinglistid when querying for contacts when it works just fine against the mailinglist directly. Im seeing this result on multiple different brands I have access to so it seems to be a more general problem, or something Ive done wrong. Anyone run into this before or have any suggestions? Cheers, Mark