To use MAC certificates for MDM, the certificate must be signed by Broadcom in order to send to Apple
ITMS 8.x
Requires Broadcom to Sign a CSR certificate file
NOTE: This procedure requires that you have an active Apple ID.
Note: The APNS certificate provided by Apple has an expiration date. Retain the Broadcom-signed CSR make the process of renewing your APNS certificate easier. If you don't have it when the time comes, simply follow the steps above to create a new CSR and have it signed.