Starting August 4 new certificate will be available via
publicKeyUrl. Previous certificate will be no longer available. Apps should always request certificate via this property. Caching this certificate will result in an error.
Apple Developer: Get ready for a new Game Center authentication certificate
More info: Apple Developer Forums
Developer:Use Game Center recommended approach with certificates.
QA engineer:Check that app behaves correctly.
PM/DM:Plan necessary updates, if needed.