In the below article it states that if you can not remember the Apple ID used for the Apple Push Cert on your server to contact Apple Developer Program Support and give them the serial number of the cert so they can look up the account. The problem is their support is a dead end. It just re-directs to the website no matter what and then to a "We are unable to process your request" error message. Does anyone know how to contact them?
If you need help with Apple Push Notification service (APNs) certificates generated in the Apple Push Certificates Portal, contact Deployment Programs Support.
If a phone number for your country or region isn't available, you can email firstname.lastname@example.org.