Our organization's Apple Push Certificate is expiring soon. I was able to renew the cert but when I try to upload the new one it says that the Identifier is different than the old cert. Will this break the push cert that has ben pushed out previously on all our deployed machines? I believe the identifier is different because I was not the one who created the current push cert. Will using my Apple ID break the current push cert? Thanks!
You MUST use the same Apple ID that was initially used, or you will need to re-enroll every device in your fleet. If you don't have access to that Apple ID, contact Apple with the identifier of the current APNs certificate. They can help you recover access with some supporting documentation.
You can't, they will all need to be re-enrolled, either manually or via DEP. I'd really recommend getting in touch with Apple, it's entirely possible to gain access to the old APNs certificate with the correct documentation and have it transferred to your new managed Apple ID.
See this thread for more information.