Oh Microsoft.. you mysterious beast.
I was recently informed by one of my Techs that he could not enroll a Windows Phone to our Hybrid Intune/SCCM setup. I found this quite strange as nothing on our end had changed significantly, well other than updating my SCCM to 1602 a few weeks prior. I tested a IOS device and it enrolled just fine.
A small diagram on how Intune in Hybrid mode should work:
The user he was trying to enroll was getting the following error on a windows phone:
Early investigating led me to checking the relevant log files for Intune, this is what i saw in the dmpdownloader.log