Apple MDM is used. It is MDM using APNs.
I made a python script that does the vendor signing part, so you don't have to use the softhinker java code.
https://github.com/grinich/mdmvendorsign
Follow MDM_Protocol pdf very carefully.
If you are following this link: http://www.softhinker.com/in-the-news/iosmdmvendorcsrsigning Then verify few things.
remove the passphrase from customerPrivateKey.pem using this command
openssl rsa -in customerPrivateKey.pem -out PlainKey.pem
Then merge your APNS certificate (for example CustomerCompanyName.pem) downloaded from the portal https://identity.apple.com/pushcert/ using this command
cat CustomerCompanyName.pem PlainKey.pem > PlainCert.pem
Now this PlainCert.pem file can be used in your server as APNS/MDM certificate.
If still there is issue,please show here your device log.
the issue may be because two reasons: