Hi Eduardo,
If you navigate to Setup-->Services and expand the Mobile Device Management section, you should see more information about the APNS cert, including the current Apple ID to which it is bound. If that is the field you are referring to when you say the ID is a number, that would indicate the previous admin entered that rather than the ID. One option is to renew the cert with a different Apple ID. This will require you contact AppleCare and have them transfer the current cert serial (viewable in the portal) to the new one. This is unfortunately not something we can facilitate from our end.
Once logged in to identity.apple.com/pushcert with that Apple ID, you should see it listed. Let me know if you have any other questions.
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Matt Shaver
System Architect
IBM
mshaver@us.ibm.com------------------------------