Can't enable device management in profile manager

I have exactly the same problem with El Capitan and Server 5.2. Whether I use the server app to try and enrol devices or use Terminal commands, it will not allow me to manage devices. Yet until about two weeks ago it was all set up and running fine. I have done no new installations on the server apart form an update (which I am suspicious of). I completely uninstalled the server app and installed a back up copy but this did exactly the same. I am going to try uninstalling server again and downloading a fresh copy of server app and installing that; but that will mean a complete set up of the server from scratch. There is clearly a problem with device manager. All other parts of profile manager function normally and it picks up users form active directory which I can manage and apply profiles to; I just can't manage devices anymore

I found out that the certificate that the server app is using has the incorrect private key associated with it, or it was corrupted. It is a real pain to alter, but I did it by exporting (from a backup) the correct private key from keychain (the worst piece of apple software ever) and then adding it by drag and drop to the server app certificates. It isn't perfect as I am still getting some certificate errors but it enabled device management again and it has been working for over a week. I changed nothing myself to cause the problem; all that happened was I updated the server app with school manager included (which we will never use) and it broke things. School manager only works with iPads that are newer. I wish apple would realise schools can't keep updating to the latest hardware - there are no funds for it

Did you go through Apple's MDM enrollment process at deploy.apple.com? Once you have your deployment certificate installed on your server, you can add devices by serial number or order number in your deployment account and begin managing your devices from the server.

Dev be very careful over the next few day I have done the same and it caused my ODM to fail. Out of interest are you using a SSL cert from a third party or not

I have exactly the same problem with El Capitan and Server 5.2. Whether I use the server app to try and enrol devices or use Terminal commands, it will not allow me to manage devices. Yet until about two weeks ago it was all set up and running fine. I have done no new installations on the server apart form an update (which I am suspicious of). I completely uninstalled the server app and installed a back up copy but this did exactly the same. I am going to try uninstalling server again and downloading a fresh copy of server app and installing that; but that will mean a complete set up of the server from scratch. There is clearly a problem with device manager. All other parts of profile manager function normally and it picks up users form active directory which I can manage and apply profiles to; I just can't manage devices anymore.