To summarize the key issue/root cause of the problem:
Apple changed base url to fetch service key and did not make it backward compatible. It affected all Apple Customers globally.
Key details about the change from Apple can be found here: https://github.com/RobotsAndPencils/xcodes/issues/83
Fivetran has an ongoing effort to provide the best service to its customers. We sincerely apologize for the trouble this may have caused you and your team.
Please let us know if you have any questions or feel free to open up a Support ticket at www.fivetran.com/support